I am entirely unimpressed with her epistemology. For beginners, not only is it an out-and-out postulate that "man's reason is competent to know all of the fact of reality" it is wrong. I hate to dig up the old Heisenberg chesnut again (since it's all too frequently thrown around by people who don't know what they're talking about) but that does nicely. If you ask me to measure two observables whose operators don't commute with an arbitrary degree of accuracy, I'm going to fail. No amount of thinking, mathematics or experiment will correct this.
Now, the natural response to this might be "Well, so what? We can't know both, but we can know something about the particle." And that's exactly right. But the point is that this is the response of a pragmatist, not an objectivist. I don't posit that all knowledge is unattainable, but some of it certainly is.
I also have a problem with the frequently touted "A is A" line. I'm not actually sure what it's supposed to illustrate. "A" is a symbol -- a human construct that doesn't live anywhere but in your head (and don't be a smartass -- yes, the graphite on your paper or the light coming out of your monitor might form the likeness of an "A", but it's your interpretation of it that gives it meaning). If the statement that "A is A" is to confer some kind of information regarding the structure of reality, and if it is at the same time only an idealistic object, then the basis for Ayn Rand's epistemology is straight-up Platonism. There are considerably more metaphysical assumptions implicit in her philosophy than is ever admitted. Really, Ayn Rand's philosophy of objectivism is just a regurgitation of platonism and rationalism. Neither work. As a few examples:
1) In constructing a mathematical space, we are at liberty to assume all kinds of dimensions, metrics, topologies, and the like. An empirical judgement was needed in order to declare that we had ought to be doing classical mechanics in euclidean 3-space. Now, Rand leaves her definition of "reason" as "that faculty by which we acquire knowledge", so this example may, on the surface, appear to do nothing for my case. The problem is the wholesale Platonism and idealism involved in Rand's philosophy. If "A is A" is supposed to confer something about reality, or any other idealistic statement or object, why do I not know, a priori, what I had ought to do when describing nature? That's a valid contention, when we consider what Platonism was designed to do:
2) Platonism was created to explain our ability to recognize things. Why is this a chair? Why is that a cow? And so on. It's answer: we recognize their immutable forms. Yeah, we recognize them because we recognize them. Thanks Plato! I think modern neurology has got this one pegged.
3) [Edit]It's only just dawned on me that our inability to know the facts of reality by thought alone undermines her metaphysics too. "Reality exists independently of our knowledge of it," says Rand. "No," says I. Since our knowledge must come experimentally, and since experiments change the thing being observed, acquiring knowledge changes reality in some small way. Reality exists without us, yes. I'd also say that we do not create reality, that things exist whether we know about them or not, but the conditions of their existence is not utterly independent of our knowledge. I'll give you that this is mostly nitpicking, and I know what she was trying to say, but I think it also means something that she was sloppy in her language.[/Edit]
Read some Hume or Rescher... they're better for your brain. People try to give Karl Popper credit for the modern scientific philosophy, and might suggest adding him to that list, and that's crap. There isn't anything Popper ever wrote about the scientific method that Darwin hadn't already done. Give the props to Chucky where they belong.
It is an experimentally confirmed fact that Dembski gets his jollies by licking the butts of cats with IBS.