David, the laws of physics seem incredible in that they are perceptible to us.
We can manipulate them, we can use them for predictions.
What does that begin to tell us in terms of their fundamental nature and how can we begin
to look at the laws of physics and see what the nature of reality is?
It's certainly the case, and I think this is now uncontroversial, that if the laws of physics
were very slightly different in almost any way, there could be no life in the universe,
no complex chemistry, and no thinking people, and therefore no one who knows the laws
So they are somehow almost infinitely special in that they allow themselves to be, as you
said, not just known, but also used, and that they were used before humans even existed
to create life and then for the human species to evolve.
Now that has been for several decades, an unsolved problem at the foundations of physics.
Why that is so, called the fine-tuning problem?
And it began in a serious way, people began to investigate this in the 1970s, the physicist
Brandon Carter, who was investigating the evolution of stars, found that if the charge on
the electron had been only a few percent different, either larger or smaller, then there
would be no complex chemistry and no opportunity for life to evolve.
So the standard take on this is that this is evidence that the laws of physics, as we
see them, are not the only ones that are instantiated in physical reality.
It's rather like the argument, you know, you win the lottery and you say, why me?
And it seems very strange that the lottery should have picked out you, and the solution
to that is you'll realize that that's not such a strange thing if you realize that a million
people entered the lottery and one of them had to win.
Or if you hit a golf ball and it lands on a blade of grass, you say, what are the odds
You know, how many blades of grass there are to deal?
But the thing that makes the fine-tuning problem more mysterious than just any old random
number like a lottery or a blade of grass is that the particular blade of grass that
landed on seems to have a purpose, seems to be tuned as they call it for our existence.
And this seems to violate the one of the first things that was realized at the beginning
of modern science, which is that humans are not especially distinguished by the laws of
physics as the center of the universe or as the purpose of the universe or anything like
that, but that everything about us is explained by laws that don't particularly refer
So the explanations that have been given are that and they're radically different.
And these are pretty much the only two explanations is that in one way we have been designed
to be special by some creator God that some people would like, or some super intelligent
species in which we're assimilate, some sort of a creative process, maybe not necessarily
a traditional God, some sort of creative process.
The other extreme are multiple universes in a cosmological sense, which each one of these
multiple universes, an infinite number perhaps, picks out different laws of physics so
that in the process of this randomized approach, one would or more would give rise to us
and we're in that universe, so it's the only one we're in, so we're asking the question
I think both of those are incapable of solving the problem.
The first one, the idea that the laws of physics were designed by someone or something,
simply raises the question that that thing also has to be fine-tuned.
It also has the very properties that we're wondering about the origin of in ourselves.
It's okay to kick the problem up a level if you then have an easier problem, but if you
have the very same problem, then that's an infinite regress.
Or it might be a harder problem if that's a non-physical thing.
Could it even be a harder problem in which case it's worse than an infinite regress?
Now the other idea, which is the one that is greatly favored by cosmologists currently,
and not entirely sure why, but it has become the prevailing theory in cosmology, is this
idea that there's an ensemble, a vast set of different universes.
Now the trouble with that, as was pointed out by Richard Feynman many decades ago, is that
if that, if the only explanation why the laws of physics seem to favor us is that if we
weren't here, we wouldn't be asking, the overwhelming majority of universes in which someone
is asking, they are only just asking, that is the universe is only just good enough.
There are many, many more universes where, for example, this room and its contents have
just sprung into existence and will disappear immediately afterwards.
And this idea that the universe could be a just one in an ensemble suffers from
the fatal flaw that most such universes that have the property of containing us only
just have it, and we're about to die because a sphere of heat is coming in at the speed
of light and will extinguish us in the next picosecond.
So that means that some principle other than just anthropic self-selection has to be responsible
for the fine tuning, and it can't be designed because that just kicks the problem upstairs.
It sounds like there's no solution because I don't got one, I'm waiting for, I'm waiting
I don't pretend to have a solution, but I think I have an argument why there can be a solution
If the solution isn't either of those two, then the solution is a law or physics.
It's a law or physics that applies in our universe, or perhaps in our universe and a
But just having, as I said, just having multiple universes doesn't solve the problem.
They would have to be multiple universes that are tuned so that most things in them don't
I think the key is that the laws of physics, as we currently conceive them, are based
on atoms and working out everything that happens from a microscopic level, but if we admit
into fundamental physics, laws about emergent properties, such as computation, one of those
may imply that we exist without being anthropocentric.
David, as we consider the laws of nature, we always try to find those which are the most
fundamental, and physicists would have us go deeper and deeper in a reductionist sense
to try to find those laws, how do you look at even approaching the problem?
What I take to be a fundamental law is one that is implicated in many other explanations,
and the most fundamental laws in physics happen to be reductionist laws, quantum theory
and the theory of relativity, although there are non-reductionist laws like the second
law of thermodynamics, even in physics, but there are other laws, the principle of evolution,
for example, which says that adaptive complexity can only arise through variation and selection
is a rigid law of nature and yet is intrinsically emergent, so that's another law, the laws
of epistemology that say that knowledge is acquired by conjecture and criticism.
So now you've given three radically different kinds of laws from fundamental physics
to biology of species, to approach to knowledge that you're saying are all fundamental,
but are radically different even in their categories.
Yes, they are all fundamental in that they are needed to explain many things, and we can't
explain everything in terms of just one of those strands.
And therefore, do you explanation is an organizing principle that can unite those?
And one of the things that looking at it this way helps with is that we can see that
laws at different levels of emergence actually mesh together into what I call the fabric
of reality into a sort of unified worldview, which we can then extend.
One of the things I'm trying to work on now is extending the theory of computation into
the theory of not just what can and can't be done with abstract objects, but the theory
of what can and can't be done with any object, which is a way of looking at physics
in the manner of the quantum theory of computation.
And remarkably, that connects not only physics and computation, but it also has all sorts
of philosophical implications, such as optimism, comes out of that theory.
Well, we certainly need some optimism, so, but I'm in a loss to see how we can get optimism
It's the generalization of the theory of computation to the rest of physics.
And the way it is linked to optimism is very simple.
If you imagine the set of all transformations, we want to transform the world into a better
Now, some of those transformations are permitted and some are not permitted by the laws
So the question is, which ones of them can we actually achieve in real life?
And the answer to that must be, according to constructor theory, that the ones that we can
achieve in real life are precisely the ones that are not forbidden by the laws of
So, if the laws of physics say we can't travel faster than speed of light, then we never
But if there isn't a law of physics that says you can't live to be 500, then living to
So what are the limitations of physical laws that will give us those ultimate constraints?
Because anything within those constraints is ultimately achievable.
So the laws of physics are not actually very onerous in regard to achieving what humans
Even traveling to another galaxy, although you can't do it in the time, fortunately,
in relativity means that your time will slow down if you travel very fast.
So if you really wanted to travel to another galaxy in your lifetime and you had the right
The things that we are accustomed to calling evils, even the ones that are deemed to be
inevitable evils like death, are actually just a matter of technology to solve.
So you look very optimistically in terms of what technology can achieve.
And this, as I said, follows from very fundamental considerations within physics.
The thing is, if there were a thing that we can't achieve, no matter what knowledge we
bring to bear, let's say it was living to 500 or something, there's no law of physics,
suppose that there's no law of physics that we can't, but we still couldn't achieve
And then if we can't achieve that, no matter what knowledge we bring to bear, then there
is another law of physics that says that we can't do that.
And that's a testable law, a testable regularity in nature is a law of physics.
So as we push forward, as we push knowledge forward, as you would like to say infinitely
forward, as we do this, as we do this, we will either make progress or discover new laws