Incremental Doubt

Posted on May 25, 2008 by Peter Turney

Richard Feynman has said many wise things about the nature of scientific research. His emphasis on the importance of doubt is very insightful:

Religion is a culture of faith; science is a culture of doubt.
[...]
I can live with doubt, and uncertainty, and not knowing. I think it’s much more interesting to live not knowing than to have answers which might be wrong.
[...]
I don’t feel frightened by not knowing things, by being lost in a mysterious universe without having any purpose, which is the way it really is, as far as I can tell, possibly. It doesn’t frighten me.

However, doubt can be taken too far (meden agan).

Eliezer Yudkowsky argued that we should doubt everything and trust nothing:

Once upon a time, there was something I trusted.
Eliezer18 trusted Science.
[...]
I trusted that if I did what Richard Feynman told me to do, I would be safe.
[...]
That’s the trust I’m trying to break in you. You are not safe. Ever.
Not even Science can save you.

This was my reply to Eliezer:

I agree with your general view, but I came to the same view by a more conventional route: I got a PhD in philosophy of science. If you study philosophy of science, you soon find that nobody really knows what science is. The “Science” you describe is essentially Popper’s view of science, which has been extensively criticized and revised by later philosophers. For example, how can you falsify a theory? You need a fact (an “observation”) that conflicts with the theory. But what is a fact, if not a true mini-theory? And how can you know that it is true, if theories can be falsified, but not proven? I studied philosophy because I was looking for a rational foundation for understanding the world; something like what Descartes promised with “cogito ergo sum”. I soon learned that there is no such foundation. Making a rational model of the world is not like making a home, where the first step is to build a solid foundation. It is more like trying to patch a hole in a sinking ship, where you don’t have the luxury of starting from scratch. I view science as an evolutionary process. Changes must be made in small increments: “Natura non facit saltus”.

One flaw I see in your post is that the rule “You cannot trust any rule” applies recursively to itself. (Anything you can do, I can do meta.) I would say “Doubt everything, but one at a time, not all at once.”

Robin Hanson said something similar:

To have the best chance of succeeding in a radical project, you should instead choose just a few related dimensions on which to make radical choices, and then make conservative conventional choices on all the other dimensions. This strategy minimizes the chance that some other project dimension will go badly wrong and take down your central radical idea with it.

I believe that science, technology, language, and culture are all governed by evolution. See:

Scientific method itself evolves. The idea “Doubt everything, but one at a time, not all at once” follows naturally from this view of science. Evolution is (usually) incremental.

I think Feynman himself would endorse the more moderate rule “Doubt everything, but one at a time, not all at once”, rather than the extreme “Never trust anything”:

The scientist has a lot of experience with ignorance and doubt and uncertainty, and this experience is of very great importance, I think. When a scientist doesn’t know the answer to a problem, he is ignorant. When he has a hunch as to what the result is, he is uncertain. And when he is pretty damn sure of what the result is going to be, he is still in some doubt. We have found it of paramount importance that in order to progress, we must recognize our ignorance and leave room for doubt. Scientific knowledge is a body of statements of varying degrees of certainty — some most unsure, some nearly sure, but none absolutely certain.

We never have absolute certainty, but there are some things about which we can be “pretty damn sure”. We give these things our conditional, temporary trust, while we focus our doubt on the current object of our attention.

We must patch and upgrade our sinking ship one plank at a time.