coberst wrote:Why is the premise "A straight line is the shortest distance between two points" self-evident. It is because this is one of the first things an infant learns and it is verified and reinforced constantly throughout life by our sensorimotor experiences.
You answered your own question: this premise is self-evident because it is precisely that--a premise. It is something that is assumed to be true for the sake of an argument or a discourse; in this case, it is axiomatically assumed so that we can build a system of geometry upon it. Its "self-evidence" is part of its very definition. It was not deemed true because it matched experience; it was MADE true because it provided a useful basis for a system of mathematics.
Its conception had nothing to do with sense-experience, in other words, and it seems rather extravagant to claim that this mathematical axiom is one of the first things an infant learns. An infant learns how to get from Point A to Point B, certainly, but unless your hypothetical infant is a child prodigy it probably won't learn to apply a vocabulary of geometry to this until elementary school.
These cognitive science theories you speak of are attractive, but it might be helpful to keep in mind that they're good for explaining some kinds of knowledge but not others. You mentioned "judgment," for example, and that seems like a useful place to apply cognitive science. But like any theory, this one is ruined when you try to make it apply to everything in sight. The one thing that Kantian rationalism has going for it, in my opinion, is that it provides a more convincing picture of where mathematics comes from. That would be my response to your claim that "ideas associated with Idealism" be discouraged--quite a sweeping statement (unless you can be specific about which ideas you have in mind). CS is good for judgments, bad for mathematical knowledge; rationalism is good for mathematical knowledge, bad for judgments.
Intellectuals in general might do well to learn how to take the best parts of each theory rather than trying to find the one that explains everything. A theory that explains everything explains nothing.