00:00:14.000 Good afternoon everyone. Thanks very much for joining us. Today we have David Deutsch,
00:00:20.240 author of the beginning of infinity and fabric of reality and physicist at Oxford,
00:00:26.080 and David will talk about truth and propositions and we have a slightly different format today
00:00:33.920 because David will be giving a kind of, this will be a conversation. So David will give a
00:00:41.440 brief couple of remarks on the topic and then we will have a discussion with David and
00:00:49.520 I think first Liberty Night we'll join into the discussion and later on we'll open it up for everyone
00:00:53.760 and with that being said I give forward to David. Thanks for joining us at the poppy society.
00:01:07.040 It's statements, propositions and truth that I'm going to muse about and the context in which I was
00:01:15.600 musing is, first of all, task is theory of truth as adopted by Poppa which is called
00:01:24.160 correspondence theory of truth and the idea is that statement is true if it corresponds to the facts.
00:01:37.200 So if I can, yes, right, now there's a statement and there is a fact and that statement is
00:01:55.600 true if and only if that that really is a dog and that's the correspondence theory of truth
00:02:08.240 and I thought it was satisfactory and I believed the Poppa's treatment of it but I started
00:02:19.840 musing further about this in conversations with looly tannett and other people and also because of
00:02:26.560 the talk that was given here by Danny Frederick about a slightly different issue whether
00:02:33.440 truth can be our epistemic aim. Not quite sure what what he meant but but in any case I realized
00:02:42.880 that my own conception of truth was somewhat flawed and I came up with some ideas to fix
00:02:49.760 it which I could have called I could have called it a simple theory that resolves all your
00:02:59.280 misgivings about truth. Of course it might not resolve all your misgivings it might not be true
00:03:08.800 or it might be true but not original to me in which case it's most likely to be found somewhere
00:03:14.720 in Poppa anyway so there's a problem what is the problem? Well for start that's not a dog
00:03:27.280 that differs from a dog in a number of really vital ways but for a start it's a cartoon no dog
00:03:34.480 actually looks like that and secondly when I say this is a dog how do you know that I'm referring
00:03:39.680 to that dog and not to some elephant that's in the room so it might be referring to the elephant
00:03:45.280 in the room and then it would be false and so I could make it more precise by saying on this page
00:03:59.760 this is a dog that's more precise but you see the point that I could go on adding qualifiers
00:04:18.000 and explanations and so on add-in for item and it still wouldn't be completely unambiguous yet
00:04:25.040 reality is completely unambiguous so how can an ambiguous thing correspond to an ambiguous thing
00:04:39.680 and so that's one thing that's the problem something that's perfect and objective
00:04:46.720 but not directly perceptible that's that's the dog how can that correspond to something
00:04:55.360 that's imperfect parochial and perceptible which is any kind of statement about a dog
00:05:02.000 anything physical is like an idea in our brain or statement in words which could
00:05:09.040 never be perfect so it can never be perfectly true nor can it be perfectly precise and perfectly
00:05:15.920 unambiguous so by the way that there's also a meta language involved in this theory of truth which is
00:05:28.880 which says something like something like that and this is true if this is a dog so that's a
00:05:49.040 statement in the meta language so there's a sort of triangle here of a statement and some reality
00:05:55.520 and a meta statement that that's Tarski's theory and another another reason why
00:06:03.680 far from being ambiguous and so on we are fallibleists we expect to improve our ideas
00:06:12.720 and so the ideas in our brains and our statements of them can't be perfect if they can be improved
00:06:18.960 so so here's what I thought might might resolve this so in addition to statements and some
00:06:33.360 reality by the way the reality could be mathematical reality in some but I'm using physical
00:06:38.320 reality because to simplify things we could be talking about prime numbers and exactly the
00:06:45.040 same issue would arise so there are some things here which there are some other things which are
00:06:55.760 perfect and pristine and beyond our reach but we can which we can nevertheless talk about and form
00:07:02.080 theories about and that is the class of abstractions something like what popular called world three
00:07:10.320 but but I just prefer to say that the class of all abstractions which include things like
00:07:16.880 you know numbers like so it's up here there's number five that's an abstraction and and again
00:07:25.920 I can't draw the number five I can only draw some marks on my iPad screen
00:07:33.040 that thing there is just a marks on a screen and it's not a it's it's not a five because
00:07:46.640 that is not a five it's a 50 even though it looks exactly like this five
00:07:51.520 so again anything I might draw or say is ambiguous and and partly wrong and and all that stuff
00:08:05.760 but the thing I'm referring to here the actual number five that's a perfectly definite thing
00:08:12.480 and and there are also up here propositions the propositions like five is a prime is a proposition
00:08:20.400 and except I just what I just said is a statement I can't say propositions it's impossible
00:08:26.640 so there are propositions up here which I'm representing so there's a p and a not p and a not
00:08:35.360 p and not p these are all propositions and these propositions and propositions have the property
00:08:43.840 that they can be true or false and nothing else absolutely nothing else says there's no
00:08:48.880 that it's the excluded middle and they're perfectly precise they're perfectly unambiguous
00:08:56.160 here are some propositions and this one is actually true I mean the proposition this one
00:09:03.040 proposition I'm referring to is actually true but unfortunately that's because it doesn't assert
00:09:07.360 anything about anything and also this p and not p strictly speaking those aren't propositions
00:09:16.480 either they stand for propositions they have propositional variables so this thing is true because
00:09:23.360 it's true regardless of what p stands for but just just this one is a propositional variable
00:09:33.440 and it stands for something that's either true or false but it itself just represents that it's a
00:09:40.960 variable by the way it's quite usually talking about the world and about ideas that we're super used
00:09:48.400 to things that stand for other things and calling the things that stand for other things the things
00:09:57.760 and sometimes we have to be careful and make sure that the like the map isn't confused with the
00:10:02.720 territory as they say but usually one can disambiguate sufficiently well but that's just another
00:10:10.160 level of ambiguity that is cannot be perfectly resolved so if I try to write down here an actual
00:10:21.440 proposition the traditional ones are things like or maybe I can change color I hope this works yes
00:10:43.040 okay so there's a traditional proposition all men are mortal and it suffers from the usual
00:10:50.080 ambiguity like like whether this refers to people who are alive at the time of Aristotle or
00:10:58.320 some things not clear whether men includes women or whether men includes men who've already died or
00:11:04.960 men who have yet to be born and and and so on so but nevertheless there is an idealization we
00:11:16.240 can think of which is that qualified by an infinite number of qualifiers as it were enough to make it
00:11:24.000 which we could never actually do in real life but this kind of represents a real proposition somewhere
00:11:32.000 in there and this proposition could be true of the world with people in it and so on and
00:11:44.640 they're either all mortal or not all mortal and then that's true if they are all mortal
00:11:55.680 so the more you try to define this the the more vague it gets but like with the five and so on
00:12:05.600 there is a real thing there a real abstract thing and and here's another real thing the world
00:12:11.200 and they could correspond with each other and my idea is that the correspondence theory of
00:12:21.840 truth refers to this correspondence the correspondence between two between an abstract thing
00:12:33.280 and a real thing both completely unambiguous and completely objective and our statements about them
00:12:41.200 are always attempts to express them well enough to solve whatever problem we're addressing so I can
00:12:48.640 can I can draw dividing line anyway if I can move this aside I can say that they're the abstractions
00:13:02.880 and then there's the the reality then there's a correspondence and then there's a
00:13:18.960 meta theory saying true if if they correspond there's the meta theory and it refers to
00:13:38.960 these are the nasty dirty things that we can actually say and this above this line is pristine
00:13:52.480 truth and the exactness and and the miracle is that we can actually gain knowledge about these
00:13:59.680 things we can say things about them never perfectly so so we have here instead of instead of just
00:14:08.800 this abstract sort of statements corresponding to reality which is what I thought task is theory of
00:14:16.160 truth or to say it's a triangle it's this this and this is a triangle and if you like this this
00:14:32.960 meta statement I have to somehow bring it out of the page to form a tetrahedron so it's
00:14:40.880 either a straight line converted to a triangle or a triangle converted to a tetrahedron and that
00:14:47.280 is my theory of truth which it is and now you can you can shoot it down great thanks so much for
00:14:57.360 yeah well the introductory statement I so for the first question I have is how can it be that the
00:15:05.840 these infinitely long propositions can be approximated by finite statements
00:15:17.120 yes I don't think there's any guarantee that they can the yes well so I think the situation is
00:15:33.680 worse than what you say because saying that the the abstract perfect thing is like the imperfect
00:15:40.960 thing with an infinite number of qualifiers I don't think there's any any guarantee that even an
00:15:46.720 infinite number of qualifiers would even if they were possible which it isn't that even that would
00:15:53.440 do so the how can we how can we expect our statements to correspond to this pristine truth well
00:16:08.480 one thing is there is no guarantee they might not be able to I argue in in my book that there
00:16:16.800 shouldn't be any limit to how well we can do this but even though we can never do it perfectly
00:16:24.960 and the the thing to remember as always with Popper is is when Popper says at least I think
00:16:33.600 when Popper says we're striving for the truth he always means we're striving to eliminate error
00:16:39.040 of course we can't be sure of that either but when we use truth as a as a value that we are
00:16:48.320 that we are aspiring to we're not aspiring to be able to utter true statements we are aspiring
00:16:56.480 to eliminate false statements from the things that we say which always leaves more false statements
00:17:03.520 and we can't be sure that we haven't eliminated a true statement
00:17:11.840 so I there is no guarantee and there's no there's no reason not just no guarantee
00:17:19.600 there's no reason in the structure of all this if if I'm right that that implies that there should
00:17:28.640 be statements that that represent an abstraction perfectly even infinitely long statements
00:17:41.920 so I don't know if that's good enough maybe it isn't but so you think that we can guess at
00:17:47.120 the correspondence between the statements and the abstractions and that is how we kind of
00:17:52.720 aim to find out about reality yes yes we guess that our statement is some is some kind of indicator
00:18:01.600 of the abstraction like if I say two plus two is four that is in the light of a whole slew of theories
00:18:09.520 that that connects statements in the English language to to integers and and then there's a theory
00:18:16.240 of integers which we can't prove true either it might be inconsistent for we know but but
00:18:24.880 somewhere in the set of all abstractions there are consistent things and we have a theory that
00:18:31.680 the set of all integers is a consistent thing and that what we say about it correspond to true
00:18:38.640 propositions about that thing and in all those ways we're bound to be inaccurate and ambiguous
00:18:47.440 but nevertheless we might have some genuine knowledge about it
00:18:54.800 right and I see people are raising their hand in the chat I also think that Liberty is a question
00:19:02.480 so let me see go ahead this might be the same as Sam's question but do you is there anything
00:19:11.280 specific in Danny Fredericks kind of skeptical view that you think this resolves
00:19:21.760 well I must say I didn't entirely understand his skeptical view it was directed against something
00:19:29.600 slightly different from what I'm talking about namely the question of whether
00:19:37.440 we can regard science or or just thinking in general as a quest for truth and he was saying we can't
00:19:45.600 now I don't I don't see that's a very important question I mean I'd rather say what we are doing
00:19:53.680 rather than say whether it's whether it's legitimate to call that a quest for the truth
00:20:00.640 but I think in the you know his was it was a much longer statement than than my musing here
00:20:07.680 I think he also touched on the problem that I'm talking about here namely that we can never
00:20:14.160 capture a proposition and true or false and that therefore we can never capture a truth
00:20:25.840 but I don't think that's important as long as we know that we're not trying to capture a truth
00:20:31.600 so we're trying to eliminate errors and I think someone asked him that and he answered and again
00:20:39.040 I didn't quite understand the answer so but but anyway I think this is this is a simpler issue
00:20:55.120 if truth is correspondence with the facts how can a statement which is incapable of being
00:21:09.040 true or false correspond to a fact which either is there or not and you know that thing in real
00:21:17.600 life there is an attribute being a dog which any given thing has or doesn't have
00:21:28.800 we can't specify that unambiguously but we can specify it unambiguously enough
00:21:39.840 and the sort of a higher level thing of whether that counts as pursuing truth
00:21:49.360 well I don't really mind I don't really mind either way
00:21:55.360 right so this is not trying to address the kind of skepticism that Danny was advocating
00:22:00.960 I don't think so then I mean you you already explained it quite well but then I still
00:22:11.600 so I understood your construction from that conversation with Danny and I I kind of sought as a
00:22:17.600 as a defense of realism and of the aim of science being the search for truth but
00:22:23.680 so I think I had a misconception about what your construction was trying to address
00:22:30.640 and so I think your problem and I think because of that misconception I also misunderstood
00:22:36.480 the problem you were trying to solve so could you explain briefly what the problem is that you
00:22:41.280 trying to address with your construction yes so given the so here we have some reality that's
00:22:51.200 pristine that that's sort of perfect and we have some abstractions which are pristine
00:22:57.120 and that's perfect and therefore it's meaningful to say that there is a perfect is or isn't
00:23:03.600 a perfect correspondence between them and and we can cook when the correspondence is perfect
00:23:10.320 we can say that this abstract proposition is true and and then there are these statements
00:23:18.400 which are riddled with error and ambiguity and and so on and the problem was how can one of these
00:23:32.880 possibly correspond to any of that right so the answer is it can't and it doesn't it's this
00:23:42.240 which corresponds to that it's this which corresponds to that and we are merely
00:23:56.400 guessing that this is that what this is and what this is and what the correspondence is
00:24:05.040 and we're just hoping that that our guesses are better than our previous guesses
00:24:09.600 right and no this doesn't our statements don't actually have to correspond to anything
00:24:18.160 in the sense in an exact sense which would be required if we're defining truth that way
00:24:23.680 right but would it be fair to say that you are defending realism oh yes but but I think
00:24:29.440 Danny would say that he's also defending reason yes but we might think he isn't yes
00:24:35.920 but I really am we we've found a big guess that you really are yes yes cool I see there's some
00:24:46.000 more people who have questions specifically looly as our hand race looly go ahead
00:24:52.800 yeah so usually we talk about abstract things which are like philosophy and maths and then
00:25:00.240 practical like down to earth things like you know this water bottle or whatever
00:25:04.000 and you're saying that all statements correspond to abstractions
00:25:10.080 is this like is this like a technical sense or is there a meaningful difference between abstract
00:25:17.280 statements and these kind of like practical statements I think it whenever we say anything
00:25:25.680 we're we're about the world let's say we're doing it via an abstraction we we don't usually
00:25:36.080 say so or even think of it in that sense but that's because of our just being totally accustomed
00:25:43.440 to having things which stand for things which stand for things which stand for things
00:25:47.600 and just just speaking as if the first one was equal to the last was the same as the last one
00:25:53.120 but in reality if you want to make sense of what theorizing means and what truth means
00:26:00.560 and and what having a theory about the physical world or about the abstract world means
00:26:07.600 then I think you've got to say well according to my theory you've got to say that that all our
00:26:15.280 statements are are referring to abstractions which refer to the thing that we're talking about
00:26:21.680 rather than just referring to the thing we're talking about
00:26:26.960 so there's no say we're saying purely abstract statement sorry so there's no such thing as a purely
00:26:33.520 abstract statement or a purely non abstract statement well there is no such thing as
00:26:42.000 yeah I see what you mean yes well we can't utter an abstraction we can only utter physical
00:26:48.240 objects like like sound waves and so on so we are purely physical and our theories are
00:26:56.800 always expressed purely physically but we can theorize about let's say the world and about abstractions
00:27:06.480 and when we say this is a dog and we say that in the context of some problem we have
00:27:14.240 then because there is no such thing as a correspondence between these statements and
00:27:26.160 real objects like physical objects like dogs but there is such a thing as a correspondence between
00:27:33.920 an abstract proposition and a physical object like a dog
00:27:37.680 therefore we must always be talking about that abstract proposition whenever we say things that
00:27:45.680 we're hoping are true or true or whatever if the concept of truth applies we must be talking
00:27:52.720 about propositions because it's only propositions that can be true or false
00:27:57.840 right then I think I have another question which is that or unless Lily wants to
00:28:07.840 expand on her question I hope I'm not interrupting if not then
00:28:15.200 your idea of the statement is that is that purely linguistic or because for example you were
00:28:24.000 talking about the cartoon dog at the beginning of the presentation and it's basically
00:28:34.400 that also seems to be in some sense a statement so it seems to be about not just
00:28:39.440 sentences that we can construct but also like the cartoon dog is a statement that corresponds to
00:28:44.560 some abstraction yes I don't know okay I hadn't thought of that you could call this dog you could
00:28:54.240 call this mark that I made here you could call that a statement because but it would normally
00:29:04.000 be called more like something like a model or a representation statements models representations
00:29:12.880 and utterances and sentences written down all those things the important thing from my point of
00:29:20.640 view here is that those are all physical objects and so they can't have the property of being
00:29:28.880 true or false right but yes this is this cartoon is for present purposes it's a statement
00:29:43.760 about a dog but I want in this context I want you to take that as if it was a real dog
00:29:49.680 so that I can talk about whether that that other statement there on the left refers to it or no
00:29:56.000 or responds to it or no but I can't no matter how I try to talk about abstractions or reality
00:30:03.440 I can't directly represent them I can only represent them as physical objects that aren't them
00:30:11.360 I see okay thanks then Charles he Charles has his hand raised go ahead
00:30:17.120 yes okay thank you hi and thank you David and I well it's not a question it's a many ideas that
00:30:30.560 I think would be quite cute to relate with other ideas of yours I recently came about the
00:30:37.200 chapter five of the fabric of reality in which you speak about the Turing principle in a very
00:30:43.520 grandiose way and namely I was kind of aware of the idea that computer programs can be put into
00:30:52.080 correspondence with simulations of physical systems but the chapter ends with the idea that
00:31:02.480 not only physical systems can be or virtual reality rendering of physical system can be given
00:31:10.080 by computer programs but also virtual reality renderings of abstract entities so all that
00:31:17.360 what mathematicians think and all all men are mortal or can be also in a sense thought of abstract
00:31:26.480 renderings well no virtual ready renderings of abstract entities so so the quest of science as
00:31:35.040 search for truth in in this context of trying to get a map between our virtual reality renderings
00:31:44.320 of the of the reality out there can actually make sense no because this is what we're kind of trying
00:31:50.800 to do to get our ideas to correspond to the physical world and let us be a well okay
00:32:00.480 I would agree with any question sorry I don't have any precise questions but I just think that
00:32:08.080 maybe it can give you the idea of commenting on this link between the Turing principle and
00:32:15.840 and this theory right here well there's no direct link in that sense I think because the
00:32:27.920 set of all things that we can represent in virtual reality is basically the set of Turing
00:32:34.160 computable functions and the the abstractions that we can speak of are a much larger set than that
00:32:46.400 we can talk about say the real numbers without making a virtual reality rendering of all real
00:32:54.000 numbers so I thought you were going to say therefore our quest to understand the abstract world
00:33:05.120 is exactly the same quest as our quest to understand the physical world and that they are both
00:33:10.880 done by by making guesses about these abstractions which are propositions and that I would have agreed
00:33:19.280 with entirely but I don't think it's the case that we are just investigating the computable
00:33:27.600 we can perfectly well investigate the non-computable but don't we investigate the non-computable
00:33:36.240 through models of real numbers yeah but that's it yeah I mean we're we're poor imperfect creatures
00:33:44.400 we also investigate it through through much more crude things than just models we investigate it
00:33:52.240 through things like neurons and moving lips and so on it's it's kind of miracle if this is maybe
00:34:01.840 an answer to Sam's question at the beginning it's maybe a kind of miracle that something so
00:34:07.360 crude and error prone as as our as the part of the physical world that we control can have such
00:34:16.880 tremendous reach not only in the physical world but into abstractions I don't think it's the case
00:34:23.760 that we are that we are limited we're limited in what we can model but but to think of knowledge
00:34:30.880 as just a model is not is not true where we can talk about things that we can't model we can
00:34:38.480 understand things that we can't model but how do we understand and if we don't give ourselves
00:34:48.800 some theory in in some virtual reality rendering of no no no real number for example yeah most
00:34:57.680 mathematicians think that that P doesn't equal NP and it could be true that P doesn't equal
00:35:05.280 and suppose it's true and suppose it's not not decidable well we can still perfectly well
00:35:12.640 have a theory that P doesn't equal NP it doesn't stop us at all the fact is undecidable
00:35:17.760 we can even argue for and against that proposition because argument isn't proof
00:35:25.520 and by the way proof is useless without explanatory argument
00:35:32.960 yeah I think that's a very nice point because obviously mathematicians and do research into
00:35:41.200 which functions are and aren't computable so they have to be able to tell something they have
00:35:46.480 to be able to describe those kinds of abstractions in some way otherwise they couldn't do
00:35:52.800 their research we couldn't be having this conversation about them right now yes and to before they
00:35:57.680 can prove anything they will have had a conjecture you know mathematician could spend 10 years
00:36:05.600 proving that such and such and such and such a proposition is undecidable but that's because
00:36:12.640 the mathematician will have had arguments in mind that not only that it is undecidable but that
00:36:21.120 there's a way of proving it and so on and if he fails to prove it he may still think it's
00:36:26.480 undecidable and I think P doesn't equal NP is a good example of how easily that can be true
00:36:33.680 everybody believes that and it could be that nobody will ever prove it
00:36:42.800 yeah Charles I'm not sure if I'm interrupting your conversation
00:36:46.240 no it's good it's good then I'll thank you about it thank thank you and that way another thing
00:36:53.200 it's just that the arithmetic of the integers is consistent again everybody believes that too
00:36:59.600 but it's unprovable yes yeah yes I think there's various paradoxes that pop up here
00:37:07.280 anyway I see there's another question in the chat by Jake I'm going to mispronounce your name
00:37:17.040 sorry Jake fourth wine I hope I said that right go ahead yeah thanks so I have a question about
00:37:25.520 this relationship between I guess I guess I could apply both to the relationship between our
00:37:30.240 statements and the abstractions and to the relationship between the abstractions and the world
00:37:35.680 I'm sort of more concerned about the relationship between the abstractions and the world
00:37:39.520 but I guess I'm wondering about what the what it would mean to say that the abstraction
00:37:45.520 corresponds to the world or even refers to the world that certain pieces of the abstraction
00:37:51.760 pick out certain things in the world and not others to refer to them and what the what the
00:37:56.640 nature of that relationship is independent of whether it's true what does it mean to even refer
00:38:01.040 yes and well you're quite right that there could be an abstraction there are abstractions out
00:38:06.160 there that don't claim anything they let's say you could have you could have the mathematical
00:38:17.280 model of the standard model of particle physics and let's suppose that that was true it still
00:38:28.320 wouldn't be an assertion so it so it couldn't whether it can whether it corresponds to anything
00:38:40.560 depends on what it's claimed to correspond to because if somebody said that claimed that
00:38:46.800 that mathematical model is a mathematical there is a mathematical model of the weather on the planet
00:38:53.360 earth then that would be false so the the claim is another abstraction so the proposition
00:39:04.400 would be something like the real world the real physical world consists of fields and particles
00:39:12.720 that obey these equations and then some equations and then that that abstraction would have made
00:39:18.800 a claim about the real world but doesn't that like threaten a kind of infinite recursion there
00:39:27.520 where it's never actually getting explained how it is that say the the the the reference of
00:39:33.920 particles picks out certain things in the world and not others I just lost David space I don't know
00:39:39.520 piece there so the question is like so it's not so much whether this description of particles
00:39:52.640 is true of the world it's what does it mean to pick out some subset of the world and designate
00:39:59.840 particles and and and therefore have this reference relationship between part of the implication
00:40:05.120 of this proposition that I'm imagining is that there is a physically real world so that's one thing
00:40:12.880 it would have to imply and then it would say that in this physical real world there are things like
00:40:19.040 electrons and then so on and they obey these equations now it could be that there that still
00:40:25.840 doesn't say what distinguishes the physically real world from from anything else and it it it it
00:40:36.560 doesn't explain why there is one and only one of those and there could be none of those or there
00:40:43.200 could be three of those or or whatever so but that's just that's just a consequence of the fact
00:40:51.760 that I can't imagine this perfectly exact proposition it doesn't say that there that in the
00:40:58.960 world are abstractions there isn't a proposition about the world which is capable of being true or
00:41:05.040 false if it's if you think of the true one then there is also just not that which is definitely a
00:41:13.760 false one though it's not an explanation because as I'm always saying the negation of an explanation
00:41:19.840 is never an explanation but the proposition which is an explanation could be true it might not be
00:41:27.040 the whole truth about the world it is just talking about the standard model in the world but that
00:41:33.280 could be true and if it claims that it is true then it's a claim about the world including
00:41:41.200 a claim that there is one and only a one world and a physical world I mean
00:41:45.200 so I just sort of one more one more related question so I guess it's not that there is a world
00:41:52.960 that seems problematic to me but the division of that into an ontology and kind of how you carve
00:41:59.040 the the joints of that ontology and if you think about like a natural language statement like
00:42:04.960 this is a dog the the reference relationship there is it could be accomplished just by appealing
00:42:12.720 to the context right so if I communicate this is a dog and you and I are in the same room
00:42:16.800 and we're having the same kind of percept of there being a dog there then the reference of this
00:42:20.960 is just going to get worked out automatically by the by the context that we share but when we're
00:42:28.720 talking about the the way reference relationships get determined between abstractions and the world
00:42:36.160 I have no idea how that would be accomplished and then I also wonder if we stay in the same
00:42:41.040 relationship to the abstractions as we stand to the world which is to say we don't have access to
00:42:44.640 them why introduce the idea of the abstractions and not just talk about an error prone contextual
00:42:51.360 problem solving relationship to the world boy when I so in the in the in the sentence this is a dog
00:43:00.240 the word this is indexical it it gets its meaning from the context the proposition that
00:43:07.760 refers to it doesn't have a physical context so it would have to explain what this is it would
00:43:15.600 have to say in the physical world there is a planet with such and such characteristics and
00:43:24.000 such and such a time defined by these physical characteristics there's a person sitting in a room
00:43:31.120 with an animal which is in fact a dog and so on but it would say all that with perfect precision
00:43:39.520 so it couldn't say anything indexical that's quite that's quite right but I think the other part
00:43:45.280 of your hesitation I think I disagree with you seem to be assuming that abstractions inherently
00:43:55.280 must refer to other abstractions they can't get out of the world of abstractions but
00:44:03.520 I think that is not so I've just given an example of something where if it says there is
00:44:08.880 there is in physical reality there is such a thing as physical reality then it is saying I mean
00:44:14.480 might be false but it's saying something that isn't de referring to just abstractions
00:44:19.600 yeah no it's not that I think that it can't the abstractions can't get outside of abstractions
00:44:27.280 I guess when you say there is a dog my question is what does it mean for that piece of the
00:44:35.920 abstraction to correspond to some particular thing in physical reality so it's not whether there's
00:44:40.000 physical reality at all it whether it comes divided into things like dogs or cups or whatever
00:44:47.440 other kind of you know every day scale if it doesn't then the proposition would be false
00:44:55.920 but then then you seem to be taking this reference relationship and bringing it back into
00:45:02.480 this truth relationship so so is everything about whether a proposition refers to the world
00:45:08.560 subsumed by whether it finally is true no because it could be asserting something false about the
00:45:16.320 world but okay but so then then I guess it but if to say that if dog doesn't pick out anything in
00:45:24.800 the world it's not true and that's why it doesn't refer to the world I guess it's not dog that doesn't
00:45:32.320 so in in my story it started off by saying there is a real physical world in that world there was
00:45:38.400 a big bang in the big bang there was a star which we shall call the sun which and so on and in each
00:45:45.680 case it gives enough context within the thing is referring to to define it uniquely and perfectly
00:45:55.200 now if at any point that doesn't correspond to reality then the proposition is false it's still
00:46:03.200 asserting something you know it could say that there is there is this planet that's loose without
00:46:12.640 a star and in that there's a person called David Deutsch who's referring to her now as soon as it
00:46:18.560 has said that it is false but it's still it's still an assertion it's still a in my imagination
00:46:29.440 a perfectly precise meaningful assertion it's it's an assertion about something which logically
00:46:39.040 could be like that but in fact isn't so so if I talk about the sun revolves around the earth
00:46:50.880 the sun has a reference in physical reality but that statement about the sun would be false
00:46:55.760 yes but this is I guess independent of whether that statement is true or false
00:47:04.480 what does it mean for the sun in that statement to refer to the thing in physical reality so
00:47:09.520 so like like what does it mean to pick out a thing in physical reality for the obstruction to refer
00:47:16.160 to say that the trick I thought of and that there are probably many other tricks is to first refer
00:47:21.600 to the whole physical reality right then define unambiguously various bits of it until you
00:47:29.920 zoom in on the one you want to talk about so in this world of abstractions something like a cup
00:47:37.040 gets built up from the whole of physical reality all the way up yeah that's one way to do it
00:47:43.040 okay okay thank you it might be a more efficient way
00:47:48.720 okay then I think Toby Jake is next Toby go ahead
00:47:55.040 yes in your book I think you wrote that there's only a finite number of abstractions that
00:48:07.520 could apply to the physical world namely the computable abstractions and countable number yeah
00:48:14.480 the countable yeah so if is it possible if there is a finite number of abstractions that could
00:48:21.680 apply to physical theories or unique physical theories that we could rescue poppers theory of
00:48:29.200 true flightness so that we can get closer to the truth because there's only a finite number of
00:48:36.480 different physical theories we could discover yeah well actually I think there's an infinite
00:48:42.560 number of physical theories it's just countably infinite rather than finite and unless you
00:48:49.200 are thinking that a finite region of the universe can only contain finitely many distinct states
00:48:58.400 which might be the case you know from the Beckenstein bound and so on so yes but I think even then
00:49:08.640 it would be pointless to resurrect poppers notion of truth likeness because
00:49:14.880 the fact that so this would allow you to sort of say whether two theories are lexicographically
00:49:27.840 close to each other in the dictionary of all possible statements but that's not what popper
00:49:33.680 meant by being close he meant the set of all implications of the one is somehow close to the set
00:49:41.600 of all implications of the other I forget how it goes it's that the true implications of one
00:49:47.440 and other than tortologies you know he was making it up in that kind of way that would still
00:49:59.040 be an infinite number and I think it would still be infinitely ambiguous it would depend on what
00:50:06.640 your purpose was in comparing these two theories one of them might be closer to the kind of
00:50:16.160 truth you want to talk about and the other one might be close to the kind of truth that someone
00:50:21.120 else wants to talk about so you know for example there's the kind of truth that that leads to
00:50:30.640 accurate predictions and then there's a kind of truth that leads to better future theories so why
00:50:38.000 bother I think that popper in the end basically said why bother as well what I had in mind was
00:50:49.040 I've noticed with theories as they've gone through time they've got they changed the kind of
00:50:55.840 invariant symmetry so we had Galileo variants then we had the rents and variants and I was
00:51:03.280 wondering if in that case if we were seeking part of airiness in theories whether that process
00:51:11.360 whether there it you know if there it there's a finite perhaps there is a finite number of those
00:51:16.400 different unique variant mathematical structures which could apply to our our universe
00:51:22.960 but that was where I was kind of facing that idea from well so first of all if there was just a
00:51:32.640 finite number but it was 10 to the 500 so we wouldn't be much better off so if there was a finite
00:51:40.080 number and some some people think that there's eventually there will be a single mathematical
00:51:47.280 object which is the only reasonable one to to theorize corresponds with the physical world
00:51:58.720 and I don't think that would be the end of the story either because there'd always be the problem
00:52:04.560 of why is that physical object physical why is that sorry abstract object physically instantiated
00:52:13.600 and not some other one it it couldn't itself contain the explanation of that
00:52:29.920 but then I kind of have a because Toby mentioned Popper's theory of truth likeness
00:52:37.360 uh do you think that with this theory of correspondence to truth that we can we can still talk about
00:52:47.120 theories containing more truth over time so I know that this is slightly different from the
00:52:51.840 problem you're trying to address and I'm kind of drawing it back to this conversation we have
00:52:55.040 with Danny Frederick on the same topic or on a related topic and yeah do you think that this
00:53:03.360 course anything I so first of all my view is that it's in some cases you can say that one theory is
00:53:14.720 unambiguously better than another theory because the the set of true implications of one of them
00:53:22.480 includes the set of true implications the other and vice versa the set of false implications is
00:53:28.000 contained in the set of false implications so that but that's not always the case and in that case
00:53:35.440 the the set of true and false propositions just overlap but if you think of it not in terms of
00:53:51.040 truth but in terms of knowledge then when we have eliminated some errors and we hope not introduced
00:54:01.120 other errors then we have unambiguously made progress regardless of what the true implications are
00:54:10.880 of the relevant theories you know when when we when we have successfully made a vaccine
00:54:21.360 that kills the disease better than all previous medicines then we have made progress
00:54:31.920 and the the question of truth doesn't really we don't really need to measure how much truth it
00:54:41.120 has it might have been built on a theory of RNA which is overturned next week but where the
00:54:54.400 overturning doesn't actually invalidate the explanations that led to the vaccine so in that case
00:55:07.040 inventing the vaccine was genuine progress as genuine growth of knowledge even though
00:55:14.400 it used a theory that was worse than the previous theory I mean maybe that's about example because
00:55:21.200 these things have lots of different theories associated with them but but you see what I mean I mean
00:55:30.480 science is about problem solving so so is life and with problems what what we want to do is
00:55:37.520 eliminate errors if we can eliminate some errors it doesn't matter how true the theory is
00:55:43.520 yes yeah I think that's a very nice reply and I also have what is kind of a definite
00:55:54.240 advocate criticism of your your theory about truth literally how I mean we say that we
00:56:04.400 confelibly guess that there is this correspondence that we for example this this is a dog
00:56:09.200 corresponds to there being a dog on the on the page and but and I think this is what trails
00:56:16.480 was alluding to there are many cases where there is a lot of ambiguity and sometimes paradoxes
00:56:24.960 that arise when we we try to write down a statement like there's various paradox where you say
00:56:30.560 something like I'm let me look it up here it's something like the smallest positive integer
00:56:37.040 not definable in on their six letters which is itself a description of that integer
00:56:47.040 and so you have this kind of self-referential paradox where the integer isn't well defined
00:56:53.760 and initially that seems to be a perfectly well defined integer I think when I first read that
00:57:03.280 sentence it go oh yeah that that must be an integer that exists but in fact it doesn't and it's
00:57:10.320 it's that there's a paradox that arises how do we know that this isn't always the case
00:57:17.920 that there is that there aren't many of these things plaguing our statements that there are
00:57:23.520 statements are much much too vague to ever can reach out into the abstractions yeah well again
00:57:33.120 we can't be sure and you know if if the integer if the arithmetic of the integer is really is
00:57:38.320 inconsistent then we're talking nonsense most of the time at least we're talking nonsense in the
00:57:46.400 sense of logical implications of what we say but not in the sense of problem solving
00:57:55.520 all our theories of false that doesn't mean they don't contain knowledge and a theory such as
00:58:05.280 why did it keep doing that can you see the dog again yeah we can see the dog again
00:58:10.560 yes sorry lost lost my last my train of thought yes I think in a way I was just re-asking
00:58:23.840 the question I asked initially and I just like the example of various paradox but yeah I think
00:58:31.360 oh yes yeah well very so that's one of many in and ambiguities that that you can accidentally
00:58:37.760 slip in a sentence from the meta language and mistake it for a sentence from the language because
00:58:45.680 we use English for both so you know it's an understandable mistake to make so when you say the least
00:58:56.000 integer not definable you should be saying definable within what language and what axioms
00:59:03.200 rather than just definable yes fineable is a meaningless concept without saying
00:59:10.000 what axioms you're defining it and what language in what you're defining it in so but that's as you say
00:59:17.120 how do we know that there aren't infinitely many ambiguities like that which render meaningless
00:59:24.720 everything we say well there could be there could be but we have good explanation a good explanation
00:59:34.640 to the effect that we are in fact eliminating errors in our ideas even if they're inconsistent
00:59:42.480 we're still eliminating errors from them yes and also we as I said it was kind of a
00:59:49.280 devil's advocate criticism because of course berries paradox is a very specific paradox like not
00:59:55.680 we and we discovered it because other sentences aren't like berries paradox right yes yes
1:00:00.640 but I I I took you to mean you know just you know that could arise creep up on us
1:00:07.280 and and there could be things that we don't know about that you could also creep up on us
1:00:11.040 yeah exactly but we still like we have discovered a particular error in case of berries paradox
1:00:18.560 and whenever those errors arise we tend to notice them and correct them and then go on to the
1:00:25.600 next thing which is which is why we learn about paradoxes like berries paradox
1:00:31.680 so yeah there's there's more questions in the chat I see Danny
1:00:37.680 or Regan go ahead ask your question if you want
1:00:40.480 otherwise Ted you know hi I have a question about mathematical truth I mean some more technical
1:00:52.320 question you mentioned earlier the p equal same p problem the possibility that this might be
1:00:57.680 an decidable at some point but leaving aside our abilities to settle those questions or not
1:01:03.680 consider the the continuum hypothesis which we know for the joint work of the other
1:01:09.120 Lenco and that is an decidable from terminal Franco set here with that same of choice
1:01:13.680 I mean that's a perfectly well-formed mathematical statement do you think that it expresses a
1:01:18.320 proposition uh which is either true or false despite being uh and decidable because there are a
1:01:25.920 lot of mathematical philosophers which think that this is just an indeterminate mathematical statement
1:01:32.240 yes so I disagree with those philosophers of mathematics
1:01:36.160 I think that a perfectly well-formed mathematical proposition is either true or false independently
1:01:45.440 of whether it is decidable or not and decidable is in any case a matter of physics so it seems to
1:01:52.480 me ridiculous to base a theory of mathematical abstractions on what physics does or does not happen
1:02:01.840 to be able to model well I mean I'm not sure whether set here is really about physics because
1:02:08.160 it postulates a lot of infinities that go beyond anything that physics might study oh that
1:02:12.960 that doesn't matter it's it's it's not that sets that have to be finite it's the it's the
1:02:20.160 method of proof so it mathematics assumes that a proof is a finite sequence of propositions
1:02:33.920 each of which are follows from the previous ones by rules of inference which are also finite
1:02:40.400 they're finitely many of them they're finitely long and so on and the proof is a finite one of
1:02:45.760 those and finite here just means can be instantiated in a physical object
1:02:55.760 so it's perfectly possible logically possible that physics is different from what the way
1:03:04.240 we think it is and that the rules of inference are really either more extensive than we think
1:03:13.440 or less extensive and it could be that the continuum hypothesis could be added as an axiom
1:03:23.920 and actually be true of something such as the infinite things that we want to talk about
1:03:34.160 P equals MPs may be a better example because the doesn't the continuum hypothesis thing rests on
1:03:40.720 the fact that there that there could be models in which it's true and models in which it isn't true
1:03:46.160 yeah I mean get all proof one side in cone proof another side right so but of course those
1:03:52.640 proofs are not final they could be mistakes found in them they they they are definitely ambiguous
1:04:01.840 so the ambiguity could be resolved one way or another and it could be that our notion of proof
1:04:07.280 a notion of infinite our notion of sets will be changed again just as they have been changed in the
1:04:14.800 past well I I'm not sure how this I mean assuming they didn't do mistakes in the proof they
1:04:22.640 are mathematical clearance so I and that deal with perfectly precise notions so I don't
1:04:27.840 exactly they are mathematical theorems given a certain set of rules of inference but those rules of
1:04:37.120 inference cannot cannot be proved to be true they might be false they are just conjectures
1:04:43.120 and there might come a time when we conjecture different rules of inference are valid
1:04:49.120 right and the second thing I wanted to ask that similar to this one is how do you think about
1:04:53.680 paradoxical sentences like the Liar sentence which asserts it's some falsity I mean
1:05:03.440 perhaps you might say that this is the object language metal language error but what would you
1:05:08.480 say if I know you have what's known as Liar cycles and I say that's what whatever professor
1:05:15.120 Doy says is false and you say that whatever I say is true so you don't have this hierarchical
1:05:19.920 you know sorry hierarchy levels but it's just a cyclic clash which cannot be so easily
1:05:26.960 solved by an object language so yes so if we jointly say things which refer to each other
1:05:36.000 and which lead to a contradiction then there is no proposition corresponding to those
1:05:41.600 right there's a proposition has to be either true or false
1:05:50.400 yeah I'm thinking that if you'd say that about the Liar sentence which doesn't have the cycle
1:05:55.040 then perhaps you would get this sort of revenge paradox and you say well this is kind of actually
1:06:00.880 what it says consider the sentence the sentence does not express a true proposition and if you
1:06:05.600 say that this is not does not express a proposition that is either true or false then in particular
1:06:10.320 is not true so you basically get it back yes that so proposition also has to be perfectly precise
1:06:19.440 and unambiguous so I I think those those kind by the way I think that particular one
1:06:27.360 is a language metal language error yeah I know I guess you can have it for the cycles that
1:06:33.520 but it's more explicit if you write you can't speak okay yeah well if something doesn't make sense
1:06:38.480 it's not a proposition okay but propositions can be true or false yes must be yeah
1:06:52.880 okay then we have another question by a porch thanks a lot for a talk there it's very very
1:06:59.760 interesting and I'm not sure if this will be a question but I'm trying to wrap my head around the
1:07:06.560 to kind of tree kind of levels let's say of you have a statement which corresponds to abstract
1:07:15.920 propositions as a kind of intermediary you could say so let's say if the statement refers to
1:07:20.960 the physical world then there will be an abstract proposition which will correspond to the physical
1:07:30.240 world in some way and I guess my question is previous though would have taught all
1:07:41.280 so I guess I'm thinking about like where are all abstract propositions have this are absolutely
1:07:47.760 necessarily true and because statements or so it's like some some of the propositions about the
1:07:58.400 physical world say will be contingent their truths will be contingent on the physical world
1:08:05.680 and and I'm not sure if there's a solid question here but I thought maybe you could
1:08:12.160 just comment on that well so the statements are always going to be vague and yes they're
1:08:20.320 continued on the physical world and their meaning is vague and they might even be somewhat
1:08:30.160 contradictory but we are guessing that they correspond to sorry no I shouldn't use the word
1:08:38.720 correspond in this context we're guessing that there is a proposition that this statement is
1:08:46.080 an approximation to which is good enough in the context of the problem that we're solving
1:08:51.760 and what we're guessing there and then we're guessing that the proposition is true as well
1:08:56.640 what we're guessing is that this exact thing the proposition corresponds exactly to this other
1:09:04.000 exact thing the the physical world we wanted to say something about the physical world but that's
1:09:11.200 the only way we can do it via statements which represent propositions which are guesses about
1:09:16.960 propositions which which then say something about the physical world usually when we when we
1:09:23.360 aren't interested in talking about truth when we're only interested in talking about the world
1:09:31.280 we can do our usual thing of talking directly about the world and saying things like dogs have
1:09:37.280 four legs and but it's it's only when somebody asks what would it mean for that to be false what
1:09:46.640 would it mean for what does it what does it mean for that to be true what does it mean for it to
1:09:51.200 be approximately true what are you doing when you try and make it more precise by saying can is
1:09:57.200 familiar is instead of dog and so on then I think you're immediately forced to talk about the third
1:10:08.160 side of that third vertex of that triangle as well and say what what we mean about it being true
1:10:15.040 is not that the statement is true it's that the problem where we're guessing that there's a
1:10:19.360 proposition there that is true okay okay and my previous kind of conception of this from like
1:10:28.160 reading your own work I'm not sure if this is exactly your idea but it's something I've
1:10:33.600 gathered from reading fabric of reality for example and beginning of infinity was that
1:10:37.920 the to say that a statement a physical object of a statement contains truth means that
1:10:47.360 the sort of the knowledge content the the information instantiated within the the sound let's
1:10:56.000 say that there's like a physical I think you referred to this as like a self similarity within the
1:11:06.160 physical world or there's like one part of the physical world that's analogous in some ways to
1:11:12.800 another and so within this conception of and so that's that's previously what I taught the
1:11:19.600 idea of truth was as well both both you're you're saying that it would actually be more that
1:11:25.200 there's a there's an abstract proposition which is in this like platonic realm
1:11:30.640 that's kind of is it is required to stand between those
1:11:35.600 or that's a sense I can't remember whether I said in either of my books that this sort of
1:11:42.720 correspondence you refer to is truth that that means for statement to be true I think I may have
1:11:50.000 said it's what it means for it to contain knowledge okay and that I would stick to now I don't
1:11:56.320 but I do think that I was a bit confused about truth in both of my books so if whatever I said
1:12:03.680 about truth has to be it has to be upgraded with this new theory that that is assume
1:12:11.120 that there isn't some some flaw in it I'm hoping that you guys will find the flaw
1:12:20.560 in time for me to not put it into my next book yeah I certainly haven't found that
1:12:26.400 thanks a lot for the talk and the answer to the question yeah thanks for your question
1:12:34.480 then I see Danny has a question Daniel Regan go ahead hi can you hear me now
1:12:40.080 sorry I say I seem to have very badly timed technical issues there the last time
1:12:45.200 I am I'm so not surprised this is a lesson of question and I'm just kind of hoping you can
1:12:49.120 clear up some stuff for me to make sure that I'm following
1:12:51.280 so we have reality and reality is perfectly precise and it is the way it is and then you have
1:12:58.640 this world of abstractions which include propositions and they are perfectly precise as well
1:13:06.000 and that is what allows things like propositions to either be true or false it's the fact that they
1:13:12.480 have this perfect precision yes and then we have the statements that we can make so when we
1:13:20.080 conjecture things we can only ever conjecture statements and then there are propositions trying to
1:13:28.080 be captured in those statements and when we you said near the start you said people want to make
1:13:37.680 we're fallibleists so we want to make progress in our ideas is that about making progress in
1:13:44.720 better capturing the like let's say the propositions with our statements or is it making progress
1:13:53.040 in the sense that you're ruling out false propositions let's say we make errors everywhere yeah
1:14:06.560 so that when we try and theorize about dogs that there's whether we're right about dogs is one
1:14:13.760 thing whether we're right about the abstract proposition through which we're talking about dogs
1:14:22.240 like you know the the the can is familiar familiar is sort of thing whether we're right right that
1:14:27.840 that is a good way of being more precise about dogs that that's another thing that we can be
1:14:33.440 wrong about and in general we are wrong and vague so right so so we we we fallibly try to guess
1:14:42.240 or try to represent fallible propositions about the world yes that I'm afraid
1:14:50.800 putting that way does sound a little bit labor doesn't it it doesn't sound like god's truth no
1:14:58.160 I can't see any way of avoiding it in the moment because of this fundamental thing that
1:15:03.440 we can't say perfectly accurate things and but the world is perfectly accurate so how can one
1:15:14.480 correspond to the other so I think this is the only possible way and very very quickly so is it
1:15:20.400 you are you saying that it's in principle impossible for a statement to ever capture perfectly
1:15:28.720 capture a proposition and the cause of the inherent a vagueness and in position in precision
1:15:36.240 that's avoidable or that's unavoidable I think it's in principle impossible so
1:15:43.760 Papa quotes and often he's saying even if by chance he were to answer the final truth he would
1:15:49.360 himself not know it I think that's actually strictly speaking false yes that was that was going to
1:15:54.960 be my my thing so it's it's right okay that's fine that's fine thank you does it also mean that
1:16:03.200 there is more progress possible than Papa imagined because we we can be even more wrong than
1:16:10.160 Papa imagined we could be in some sense just Papa did think good point yeah yeah I think that's
1:16:15.840 true nice then just just for people now I think we have roughly another 10 minutes
1:16:27.920 and then we will end the event so we're approaching final questions but not yet we're not yet there
1:16:38.000 I see there are more people in the chat we have a race hand Ernst would you like to ask a question
1:16:44.160 yeah thank you so my question is sort of only tangent let tangentally related to this theory
1:16:58.080 so it's about sort of how to think about rational action in the face of ignorance
1:17:04.240 like now in this during last year and so on there was a lot of ignorance and a lot of actions
1:17:11.040 and a lot of mistakes and then nothing to live I don't know how much you know about him but he
1:17:19.200 he's a sort of admirer of popper but he takes in my understanding of him he takes the popper
1:17:26.240 uncertainty and to mean something mathematical whereas and to translate it is the some kind of
1:17:35.040 probabilities whereas that would be a mistake yeah that's a that's a mistake so so but his argument
1:17:44.560 about okay when there is uncertainty like do I do I know if this pilot is a trained pilot or not
1:17:52.960 if that answer uncertainty exists then you shouldn't get into the plane but of course we're
1:17:59.520 always uncertain so that can't be the explanation but how do you think about this how to
1:18:10.480 think about actions when we don't know what this true I'm tempted to say once you stop thinking
1:18:19.040 terms of probability all the problems go away you have a certain explanatory theory about how
1:18:30.640 this person in the uniform that's getting into the cockpit of the plane got there and the reason
1:18:37.600 that you adopt that theory and act in exactly the same way that you would act if you were
1:18:45.040 certain that it was true which you can't be but it is that that all the other explanations
1:18:55.280 is not that you can rule out all the other explanations but all the other explanations that you
1:18:59.920 can't rule out are bad explanations they are all of the form well it could be that the real pilot
1:19:08.400 was mugged on the way here and and this guy is actually a fantasies who thinks he's a pilot
1:19:15.120 but will actually crash the plane as soon as it takes off now the thing is I just made that up
1:19:20.800 I could make up lots of stories some of which would mean that you were even safer than you thought
1:19:27.440 and some of which were where where where where you'd be in even more danger than that and it
1:19:32.960 will be bad explanations because they can all be just made up at will any number of them you have
1:19:39.680 to reject all explanations like that not because they're unlikely but because the practice of
1:19:46.960 adopting one of them in preference to the others is irrational so it's good explanations all the way
1:19:55.680 down so then when we don't have good explanations well if if we don't have good explanations then
1:20:04.640 then we have inadequate explanations if we have only bad explanations then we don't know anything
1:20:14.240 where we're just in trouble it's like saying you know I'm either going to kill you or not
1:20:18.640 depending on whether you say AOB now say something well you know if you don't know you don't know
1:20:24.240 there isn't a right thing to do but the cases you're talking about like like decisions about the
1:20:30.160 pandemic are cases where we have some some explanations that aren't good good enough in the sense
1:20:40.400 that they are the only good explanation left that the others can all be ruled out by one argument or
1:20:46.480 another or that the rival explanations are all bad but we have two or three or a hundred fairly
1:20:57.120 good explanations but the others can't be ruled out well in that case there is more than one
1:21:10.960 reasonable way to behave different people will see this spectrum of a hundred decent but
1:21:18.720 but by no means good enough explanations and their background knowledge and and other theories
1:21:26.000 will select between them that is we will differ as to how good good explanations are
1:21:34.080 we might agree on what's the bad explanation but we may not agree on how good the good
1:21:41.600 explanation is and and then there are other considerations like we mustn't make choices
1:21:51.600 that will prevent us from learning things but of course we don't want to use that as
1:21:59.600 their own criterion because if we learn something by wiping out half the human race
1:22:05.600 yes okay the other half will be well off then but the half that our killed will still be killed
1:22:11.760 so so that's just one of the considerations that come into the situation that there's more than
1:22:23.600 one reasonable choice and I've been tweeting a lot about choices in the pandemic situation
1:22:31.920 and quite often the point I'm trying to make is that people are getting very upset
1:22:36.240 and enraged with each other because they think that the other person's explanation isn't as good
1:22:43.040 as theirs but they don't have an actual scientific argument or scientific evidence or
1:22:50.480 watertight argument that says that they just think it's true for some reason or another
1:22:58.960 sometimes people think that bad explanations are actually good but that's not what I'm talking
1:23:04.320 about I'm talking about disputes about rival good explanations like masks work how well do masks
1:23:15.360 work and now there's really no evidence about how well masks work it stands to reason
1:23:23.280 that masks work up to a point but then there are issues like we ask but if the government says
1:23:29.280 that people should wear masks then people will get correspondingly more lax in their other
1:23:35.680 distancing behavior and the net effect will be worse and there's no way that science can't answer
1:23:43.040 that question just yet and it won't be able to answer it in time but reasonable people can disagree
1:23:50.400 and that's what we have to do we have to disagree
1:23:57.680 all right thank you all right thank you for your question and then we have Mike Skeba
1:24:06.080 go ahead all right hi David thank you Sam so yeah early on the discussion you mentioned
1:24:12.960 P and NP and and you described P as like a propositional variable which yeah I think it's an
1:24:20.720 interesting concept and I was wondering that that was a different P oh sorry a different P in the
1:24:27.360 in terms of the NP yeah yeah so or P or not we were you saying we still have it all
1:24:31.840 P that's here in this in this that that's not P and NP that's just P a propositional variable
1:24:39.360 okay yes I that yeah my mistake and yeah I guess I kind of seasoned on that propositional variable
1:24:46.800 idea I was wondering if based on kind of the centrality of the laws of physics in your world view
1:24:53.600 and and assuming that there is not really a finality that we can speak to of the laws of physics
1:24:58.960 if you would describe them as a propositional variable kind of in this sense of statements and
1:25:03.840 abstractions I was wondering if there was a link potentially there so yeah so I I tend to
1:25:12.480 regard statements about the world and statements about abstractions uniformly
1:25:19.360 were fallible in both cases we can make mistakes we are
1:25:26.800 we are inherently imprecise and all that stuff but we can there's no limit to how much
1:25:33.680 knowledge we can know about so P the P versus NP thing is an example of an actual proposition which
1:25:42.960 could that this P the the the propositional variable could be set equal to P the actual proposition
1:25:50.880 about about computability so yeah I I view them all as the same kind of thing we can guess
1:26:07.840 about mathematics mathematical objects we can guess about sets we can guess about the physical
1:26:15.040 world we can guess about morality we can guess about beauty and all those things we can gain
1:26:21.520 knowledge about we gain it in the same way nothing is ever certain including the most mathematical
1:26:28.880 things and including propositions about necessary truths how knowledge of them is always fallible
1:26:36.880 as well no that's helpful yeah just because knowing yeah the laws of physics and what they mean in
1:26:42.640 like your momentous dichotomy just that that is also you know qualifies in that in that range too
1:26:48.560 so thank you great okay then I have a final question before we end the talk so in in your
1:26:59.440 construction there's really two worlds there's the world well it seems like there's three worlds
1:27:03.280 there's the world of statements propositions and reality and statements are part of physical reality
1:27:10.960 yes and we are guessing at both of them in a sense we're guessing at this statements
1:27:18.080 and we're guessing at reality yes through guessing at statements yes and so part of what we do when
1:27:25.520 we we try to learn about something is being as precise as necessary yeah do you think that this means
1:27:32.160 that paradoxes have a problem that can be resolved their problems with how we think about the
1:27:37.280 abstraction so if someone says if someone utters the the liars paradox they're really they're
1:27:42.320 being in precise but they're meaning something real and they we can make progress in
1:27:48.720 are thinking about the propositions as well yeah I think it's very rare for people to intentionally
1:28:00.000 talk nonsense you know no doubt it could be done and no doubt it is done in some circumstances but
1:28:07.520 but basically when people talk nonsense it's because they really mean something and that nonsense
1:28:14.320 is is actually an attempt to understand the world or to understand an abstraction or whatever
1:28:22.080 and and at the other end of the scale as as I keep saying we might all be talking nonsense
1:28:31.040 if things like the the integers are rhythmically integers is inconsistent so yeah is that what you
1:28:42.880 meant I mean yes I think I meant that when people so there's a sense in which we can
1:28:51.520 resolve a paradox when someone if we ever stumbled upon a paradox in formulating physics or something
1:29:01.200 then there is a way of of being more precise and being yes the resolving of the resolving
1:29:07.040 the issue yes yes yes yes the abstractions accidentally hitting on a paradox is just one of the many
1:29:13.200 ways we can be mistaken great great yeah with that thanks so much for joining us this was great
1:29:21.520 thanks everyone for the question for thanks for having me yeah okay thanks so much and see you
