I'm sure that throughout the 100,000 odd years of our species existence, and even before
our ancestors looked up at the night sky and wondered what stars are. Wondering therefore
how to explain what they saw in terms of things unseen.
Okay, so most people only wondered that occasionally, like today, in breaks from whatever
normally preoccupied them. But what normally preoccupied them also involved, yearning to know,
they wished they knew how to prevent their food supply from sometimes failing and how they
could rest when they were tired without risking starvation. Be warmer, cooler, safer,
in less pain. I bet those prehistoric cave artists would have loved to know how to draw better.
In every aspect of their lives, they wished for progress just as we do, but they failed almost
completely to make any. They didn't know how to. Discoveries like fire happened so rarely that from
an individual's point of view, the world never improved. Nothing new was learned. The first clue to
the origin of starlight happened as recently as 1899 radioactivity. Within 40 years, physicists discovered
the whole explanation expressed as usual in elegant symbols. But never mind the symbols. Think how
many discoveries they represent, nuclei and nuclear reactions, of course, but isotopes,
particles of electricity, antimatter, neutrinos, the conversion of mass to energy, that's
E equals MC squared, gamma rays, transmutation. That ancient dream that had always eluded
the alchemists was achieved through the same theories that explained starlight and other
ancient mysteries and new unexpected phenomena, that all that discovered in 40 years had not been
in the previous 100,000 was not for lack of thinking about stars and all those other urgent
problems they had. They even arrived at answers such as myths that dominated their lives, yet
bore almost no resemblance to the truth. The tragedy of that protracted stagnation
isn't sufficiently recognized, I think. These were people with brains of essentially the same
design that eventually did discover all those things, but that ability to make progress remained
almost unused until the event that revolutionized the human condition and changed the universe,
or so we should hope because that event was the scientific revolution ever since which our
knowledge of the physical world and of how to adapt it to our wishes has been growing relentlessly.
Now, what had changed, what were people now doing for the first time that made that difference
between stagnation and rapid open-ended discovery? How to make that difference is surely the most
important universal truth that it's possible to know and worryingly, there's no consensus about
what it is, so I'll tell you, but I'll have to backtrack a little first before the scientific
revolution. They believed that everything important, noable, was already known, enshrined in
ancient writings, institutions, and in some genuinely useful rules of thumb which were however
entrenched as dogmas along with many falsehoods, so they believed that knowledge came from authorities
that actually knew very little and therefore progress depended on learning how to reject the authority
of learned men, priests, traditions, and rulers which is why the scientific revolution had to have
a wider context, the enlightenment, a revolution in how people sought knowledge, trying not to
rely on authority, take no one's word for it, but that can't be what made the difference.
Authorities had been rejected before many times and that rarely, if ever, caused anything
like the scientific revolution. At the time, what they thought distinguished science was a radical
idea about things unseen, known as empiricism. All knowledge derives from the senses.
Well, we've seen that that can't be true. It did help by promoting observation and experiment,
but from the outset it was obvious that there was something horribly wrong with it.
Knowledge comes from the senses in what language, certainly not the language of mathematics,
which Galileo rightly said, the book of nature is written. Look at the world, you don't see
equations carved on mountainsides. If you did, it would be because people had carved them.
By the way, why don't we do that? What's wrong with us?
Empiricism is inadequate because scientific theories explain the scene in terms of the unseen.
And the unseen, you have to admit, doesn't come to us through the senses. We don't see
those nuclear reactions in stars. We don't see the origin of species. We don't see
the curvature of spacetime and other universes, but we know about those things. How?
Well, the classic empiricist answer is induction, the unseen resembles the scene.
But it doesn't. You know what the clinching evidence was that the spacetime is curved.
It was a photograph, not of spacetime, but of any clips with the dot there rather than there.
The evidence for evolution, some rocks, and some finches. And parallel universes, again,
dots there rather than there on a screen. What we see in all these cases,
bears no resemblance to the reality that we conclude is responsible. Only a long chain of theoretical
reasoning and interpretation connects them. Ah, say creationists. So you admit it's all interpretation.
No one's ever seen evolution. We see rocks. You have your interpretation. We have ours.
Yours comes from guesswork, ours from the Bible. But what creationists and empirists,
both ignore, is that in that sense, no one's ever seen a Bible either. That the eye only detects
light, which we don't perceive, brains only detect nerve impulses. And they don't perceive even
those as what they really are, namely electrical crackles. So we perceive nothing as what it really
is. Our connection to reality is never just perception. It's always, as Karl Popper put it,
theory laden. Scientific knowledge isn't derived from anything. It's like all knowledge,
it's conjectural, guesswork. Tested by observation, not derived from it.
So were testable conjectures the great innovation that opened the intellectual prison gates?
No. Contrary to what's usually said, testability is common in myths and all sorts of other
irrational modes of thinking. Any crank claiming the sun will go out next Tuesday has got a
testable prediction. Consider the ancient Greek myth explaining seasons. Hades, God of the
underworld, kidnaps Persephone the goddess of spring and negotiates a forced marriage contract,
requiring her to return regularly and let her go. And each year she is magically compelled to
return and her mother Demeter, goddess of the earth, is sad and makes it cold and barren.
That myth is testable. If winter is caused by Demeter's sadness, then it must happen everywhere on
earth simultaneously. So if the ancient Greeks had only known that Australia is at its warmest
when Demeter is at her saddest, they'd have known that their theory is false. So what was wrong
with that myth and with all pre-scientific thinking? And what then made that momentous difference?
I think there's one thing you have to care about and that implies testability,
the scientific method, the enlightenment and everything. And here's the crucial thing
that is such a thing as a defect in a story. I don't just mean a logical defect. I mean a bad
explanation. What does that mean? Well, explanation is an assertion about what's there
unseen that accounts for what's seen. Because the explanatory role of Persephone's marriage contract
could be played equally well by infinitely many other ad hoc entities. Why a marriage contract?
And not any other reason for regular annual action. Here's one. Persephone wasn't released,
she escaped and returns every spring to take revenge on Hades with her spring powers.
She calls his domain with spring air, venting heat up to the surface creating summer.
That accounts for the same phenomena as the original myth. It's equally testable. Yet what it
asserts about reality is in many ways the opposite. And that's possible because the details of
the original myth are unrelated to seasons except via the myth itself. This easy variability
is the sign of a bad explanation. Because without a functional reason to prefer one of
countless variants, advocating one of them in preference to the others is irrational.
So for the essence of what makes the difference to enable progress, seek good explanations,
the ones that can't be easily varied while still explaining the phenomena.
Now our current explanation of seasons is that the Earth's axis is tilted like that.
So each hemisphere tilts towards the sun for half the year and away for the other half.
It's better to put that up. That's a good explanation.
Hard to vary because every detail plays a functional role. For instance, we know independently
of seasons that surfaces tilted away from radiant heat are heated less and that a spinning sphere
in space points in a constant direction. And the tilt also explains the sun's
angle of elevation at different times of year and predicts that the seasons will be out of
phase in the two hemispheres. If they'd been observed in phase, the theory would have been refuted.
But now the fact that it's also a good explanation, hard to vary, makes the crucial difference. If
the ancient Greeks had found out about seasons in Australia, they could have easily varied their
myth to predict that. For instance, when Demetto's upset, she banishes heat from her vicinity
into the other hemisphere where it makes summer. So being proved wrong by observation and changing
their theory accordingly still wouldn't have got the ancient Greeks one jot closer to understanding
seasons because their explanation was bad, easy to vary. And it's only when an explanation is
good that it even matters whether it's testable. If the axis tilt theory had been refuted,
its defenders would have had nowhere to go. No easily implemented change could make that tilt
cause the same seasons in both hemispheres. The search for hard to vary explanations
is the origin of all progress. It's the basic regulating principle of the enlightenment.
So in science, two false approaches, blight progress, one's well known, untestable theories. But
the more important one is explanationless theories. Whenever you're told that some existing
statistical trend will continue but you aren't given a hard to vary account of what causes that
trend, you're being told a wizard did it. When you're told that carrots have human rights because
they share half our genes but not how gene percentages confer rights wizard. When someone
announces that the nature, nurture debate has been settled because there's evidence that a given
percentage of our political opinions are genetically inherited. But they don't explain how
genes cause opinions. They've settled nothing. They're saying that our opinions are caused by
wizards and presumably so are their own. That the truth consists of hard to vary assertions
about reality is the most important fact about the physical world. It's a fact that is itself