> I'll submit either truth is a definition, or it must be derived from something (like mathematics or science). [...] If you somehow set out to derive the meaning of truth through mathematics (or science), then to avoid assuming what you're setting out to prove, your derivation must contain no truth.

As someone who regards himself as a scientist, I'm quite happy to just say, "I don't know how to derive the meaning of truth" and move on. Saying "I don't know" isn't spouting a baseless opinion.

We've got enough of an operating understanding of what truth means to function. You do, too. If I punch you in the face and then tell you I didn't, you'll still be mad at me, because you know the truth. Perhaps neither of us can derive the meaning of truth, but it would seem that for practical purposes, deriving the meaning of truth isn't particularly important.

To be clear, what I'm saying here is that philosophers don't know either. Your argument is basically "other fields aren't experts on this thing, therefore philosophers are". No, they aren't. You've actually come closer to making an argument that the derivation of truth is unknowable than that philosophy knows anything about the derivation of the meaning of truth.

> If it is a definition, then the mathematicians and scientists are also spouting "baseless opinions" along with the philosophers, and trust me, everything the mathematicians and scientists said came out of a philosopher's mouth first, probably hundreds of not thousands of years ago.

That's a purely semantic trick. Thousands of years ago, the fields of mathematics and science weren't developed enough to be separate fields, so you could just as easily call those early thinkers mathematicians and scientists as you could philosophers. The thing is, a lot of ideas from thousands of years ago are just regarded as wrong. Pythagoras identified as a philosopher as much as Plato or Aristotle, but given the Pythagorean theorem has stood the test of time, mathematicians are happy to consider him as one of their own today. But neuroscientists aren't rushing to claim Plato because his idea of the separation of mind and body is flatly wrong. If any of those early thinkers are considered purely philosophers today, it's only because no other fields want them. Philosophy today is the leftover dregs of all the other fields splitting off as they matured.

> Sure. There's about as much basis for a material assumption as an idealistic one. The only difference is whether you're willing to assume, with ability to verify or falsify, the notion that an objective reality exists. This is of course a popular thing to believe, but it's ultimately an article of faith.

There's a basis for the material assumption in usefulness. Materialist beliefs let us reason about the world, and predict things. Going back to a previous example: we can both predict that if I punch you in the face it will hurt. You can't even reasonably argue with me on this, because even you don't disbelieve the materialist assumption with regards to this.

The idealist assumption arrives at no such result. You can claim that a mind exists separately from the body and the only thing that assumption allows you to do is get a philosophy degree.

EDIT: To be clear, if we ever meet in person, I will not punch you in the face. That's meant to be a clear example, not a threat. :)