Human beings are universal knowledge creators: they can create any knowledge that any other knowledge creator can create.

In what sense do you mean this exactly,

Another way of saying it is that human beings can solve any problem that can be solved. Does that help?

and what evidence for it do you have?

Careful here - as I mentioned above, evidence never supports a theory, it just provides a ready stock of criticisms of rival theories. Let me give you an argument: If you hold that human beings are not universal knowledge creators, then you are saying that human knowledge creation processes are limited in some way, that there is some knowledge we cannot create. You are saying that humans can create a whole bunch of knowledge but whole realms of other knowledge are off limits to us. How does that work? Knowledge enables us to expand our abilities and that in turn enables us to create new knowledge and so on. Whatever this knowledge we can't create is, it would have to be walled off from all this other expanding knowledge in a rather special way. How do you build a knowledge creation machine that only has the capability to create some knowledge? That would seem much much more difficult than creating a fully universal machine.

I've spoken to people like Elliot, but all they said was things like 'humans > can function as a Turing Machine by laboureously manipulating symbols'. > Which is nice, but not really relevant to anything in real-time.

I don't know what point Elliot was answering here, but I guess he is saying that humans are universal Turing Machines and illustrating that. He is saying that humans are universal in the sense that they can compute anything that can be computed. That is a different notion of universality to the one under discussion here (though there is a connection between the two types of universality). Elliot agrees that humans are universal knowledge creators and has written a lot about it (see, for example, his posts on The Fabric of Reality list).

On a more general note, you should probably try to be a little clearer: 'conjectures and refutations' doesn't really pick out any particular strategy from strategy-space,

'Conjectures and refutations' is an evolutionary process. The general methodology (or strategy, if you prefer) is: When faced with a problem try to come up with conjectural explanations to solve the problem and then criticise them until you find one (and only one) that cannot be knocked down by any known criticism. Take that as your tentative solution. I guess what you are looking for is an explanation of how human conjecture engines work? That is an unsolved problem. We do know some things, eg: no induction is involved.

and neither does the phrase 'explanation' pick out anything in particular.

Explanations are valuable: they help you understand something. Are you looking for an explanation of how we generate "explanations"? Again, unsolved problem.

Additionally, 'induction' is sufficiently different from what people normally think of as myths that it could do with some elaboration.

It's not really different. It's something that people believe is true that in fact isn't. Hume was the first to realize that there was a "problem of induction" and philosophers have for years and years been trying to justify induction. It took Karl Popper to realize that induction isn't actually how we create knowledge at all: induction is a myth.

Similarly, some of these issues we do take seriously; we know we're fallible,

Yes, you are called "Less Wrong" after all! I was off-beam with that.

and it sounds like you don't know what we mean by probability.

Actually, I am quite familiar with the Bayesian conception of probability. I just don't think probability has a role in the realm of epistemology. Evidence does not make a theory more probable, not even from a subjective point of view. What evidence does, as I have said, is provide a stock of criticisms against rival theories. Also, evidence only goes so far: what really matters is how theories stand up to criticism as explanations. Evidence plays a role in that. I am quite happy to talk about the probability of events in the world, but events are different from explanatory theories. Apples and oranges.