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TimS comments on Making Beliefs Pay Rent (in Anticipated Experiences) - Less Wrong

110 Post author: Eliezer_Yudkowsky 28 July 2007 10:59PM

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Comment author: TimS 04 February 2012 04:50:31AM *  0 points [-]

For me the principle of falsifiability is best understood as a way of distinguishing scientific theories about the world from other theories about the world. In other words, falsifiability is one way of defining what science is and is not. A theory that does not constrain experience ("God works in mysterious ways") is not a scientific theory because it can explain any occurrence and is therefore not falsifiable.

Because falsifiability is a definition, not a theory about the world, there's no reason to think it can be falsified. The definition could be wrong by failing to accurately or usefully define scientific theory, but that's conceptually different.

Comment author: Jayson_Virissimo 04 February 2012 09:00:39AM *  0 points [-]

For me the principle of falsifiability is best understood as a way of distinguishing scientific theories about the world from other theories about the world. In other words, falsifiability is one way of defining what science is and is not. A theory that does not constrain experience ("God works in mysterious ways") is not a scientific theory because it can explain any occurrence and is therefore not falsifiable.

Because falsifiability is a definition, not a theory about the world, there's no reason to think it can be falsified. The definition could be wrong by failing to accurately or usefully define scientific theory, but that's conceptually different.

Falsifiability is a very bad way to define science (or scientific theories). If falsifiability was all it took for a theory to be scientific, then all theories known to be false would be scientific (after all, if something is known to be false, it must be falsifiable). Do we really want a definition of science that says astrology is science because it's false?

Comment author: JoachimSchipper 04 February 2012 09:49:55AM 0 points [-]

Astrology does seem to consist of scientific hypotheses.

Comment author: Jayson_Virissimo 04 February 2012 11:02:28AM 0 points [-]

Astrology does seem to consist of scientific hypotheses.

I chose astrology because it has a reverse halo effect around here (and so would serve me rhetorically). Feel free to replace it with any other known to be false set of propositions.

Comment author: TimS 04 February 2012 05:31:25PM 0 points [-]

I agree that falsifiability is not a complete definition. My point was only that falsifiability is not applicable to the principle of falsifiability, any more than it applies to mathematics.

That said, Newton's physics and geocentric theories are false. Are they not science simply for that reason?

Comment author: Jayson_Virissimo 05 February 2012 06:21:48AM *  0 points [-]

I agree that falsifiability is not a complete definition. My point was only that falsifiability is not applicable to the principle of falsifiability, any more than it applies to mathematics.

Yes. Falsifiability is a poor definition of science and is self-undermining in the sense that it can't pass its own test.

That said, Newton's physics and geocentric theories are false. Are they not science simply for that reason?

Of course not. I'm not claiming a scientific theory must be true. I'm claiming that known falseness (which implies falsifiability) is not a sufficient condition for being scientific.

Comment author: TimS 06 February 2012 12:46:37AM 0 points [-]

A theory that does not constrain experience ("God works in mysterious ways") is not a scientific theory because it can explain any occurrence and is therefore not falsifiable.

That statement does not itself constrain experience. That's not a useful critique of the statement.

I'm claiming that known falseness (which implies falsifiability) is not a sufficient condition for being scientific.

Know falseness is not really same thing as falsifiability. Known falseness is useless in deciding whether a theory is scientific. Both the Greek pantheon and geocentric theories are known to be false.

Falsifiability is simply the requirement that a scientific theory to list things that can't happen under that theory. Falsifiability says scientific theory don't look for evidence in support, they look for evidence to test the theory.

The fact that no false statements appear doesn't mean that the scientific theory isn't falsifiable. The fact that every statement of a theory has been true does not mean that the theory is falsifiable.

Comment author: gwern 06 February 2012 01:50:19AM 2 points [-]

That statement does not itself constrain experience. That's not a useful critique of the statement.

That doesn't seem true. The statement seems to perfectly constrain experience: you will not experience situations where theories which do not constrain experience will still be falsified.

And indeed, watching the world go by over the years, I see theories like 'Christianity' or 'psychoanalysis' which do not constrain experience at all have yet to be falsified - exactly as predicted.

Comment author: TimS 06 February 2012 02:32:17AM 0 points [-]

Fine, you want to be contrary. What experience would falsify the partial definition of scientific theory that I have labelled "the principle of falsifiability"? If no such experience exists, does this call into doubt the usefulness of the principle?

Comment author: gwern 06 February 2012 02:40:05AM 1 point [-]

What experience would falsify the partial definition of scientific theory that I have labelled "the principle of falsifiability"?

Are you even trying here? Here's what would falsify falsifiability: observing superior predictions being made by unfalsifiable theories, theories which have no reason to work but which do. Imagine a Christianity which came with texts loaded with prophetic symbolism which could be interpreted any way and is unfalsifiable, but which nevertheless keep turning out literally true (writes my hypothetical self, as he is tormented by Satanic wasps with the faces of humans prior to the sea turning into blood or something like that). In such a universe, falsifiability would be pretty useless.

Comment author: Jayson_Virissimo 06 February 2012 08:56:28AM *  0 points [-]

Know falseness is not really same thing as falsifiability. Known falseness is useless in deciding whether a theory is scientific. Both the Greek pantheon and geocentric theories are known to be false.

Falsifiability is simply the requirement that a scientific theory to list things that can't happen under that theory. Falsifiability says scientific theory don't look for evidence in support, they look for evidence to test the theory.

The fact that no false statements appear doesn't mean that the scientific theory isn't falsifiable. The fact that every statement of a theory has been true does not mean that the theory is falsifiable.

Nothing in this reply contradicts anything I have asserted. I was merely claiming that if falsifiability is a sufficient condition for a hypothesis to be "scientific", then all theories known to be false are scientific (because if we know they are false, then they must be falsifiable). I'm not being contrarian; I'm pointing out a deductive consequence of the very definition of falsifiability that you linked to. Hopefully this closes the inferential distance:

  • If a hypothesis is falsifiable, then it is scientific.
  • If a hypothesis is known to be false, then it is falsifiable.
  • Therefore, if a hypothesis is known to be false then it is scientific.

I am merely denying the first premise via reductio ad absurdum, because the conclusion is obviously false (and the second premise isn't). If you took my claim to be something other than this, then you have simply misread me.

Comment author: TimS 06 February 2012 02:59:51PM 1 point [-]

That's much clearer. I didn't intend to assert that falsifiability was a sufficient condition for a theory being scientific, only that it is a necessary condition. That's what I mean by saying it was a partial definition.

Thus, I don't intend to assert the first sentence of your syllogism. Instead, I would say, "If a hypothesis is not falsifiable, then it is not scientific." Adding the second statement yields: "If a hypothesis is know to be false, then it might be scientific." That's a true statement, but I don't claim it is very insightful.

Comment author: nshepperd 06 February 2012 10:39:35AM *  1 point [-]

*shrug*

I don't think the current line of enquiry is particularly useful.

"Astrology works" is a scientific theory to the degree that it is, in fact, acceptable science to do an experiment to see whether or not astrology has predictive power. It's rhetorically inaccurate to say that means "astrology is science" though, because of course the practice of astrology is not. But sure, it's probably a good idea to include other conditions. Excessively unlikely (or non-reductionist?) hypotheses could be classified as non-scientific, for the simple reason that even considering them in the first place would be a case of privileging the hypothesis.

None of this contradicts falsifiability being "a way of distinguishing scientific theories about the world from other theories about the world", if we have other ways of distinguishing scientific from non-scientific, such as "reductionism".