What is truth, and how can we know that it is not an illusion?

Truth is a property that some propositions have and some do not. Itcan be hard to tell which a proposition is. But this much we can say.The proposition that Wittgenstein was Jewish is true if, and only if,Wittgenstein was Jewish. The proposition that Frege was Catholic istrue if, and only if, Frege was Catholic. And so forth. Somephilosophers (Paul Horwich, Scott Soames) think that's about all thereis to be said about truth. I'd disagree, but I hope we can all agreethat, even if that's not all there is to be said, it is somethingthat there is to be said. (Note that there is some kind of sense herealready in which what is true depends upon how things are. For example,whether the proposition that Russell was German is true depends upon,well, whether Russell was German, and that's a question of how things are "out there".)

So, that said, how can we know that truth is not an illusion?The obvious way to interpret the question is: How can we know, e.g.,that it isn't an illusion that it is true that Wittgenstein was Jewish?But that essentially reduces, given what I just said, to the question how we can know that it isn't an illusion that Wittgenstein was Jewish, that is, how we can know that Wittgenstein was Jewish. There's a big issue there, namely, the problem of skepticism, but that's not really a question about truth. And skepticism is rather too big a problem for one note.

I'm with Richard here: the truth of a proposition cannot be an illusion. In an illusion, the proposition is false. But there might nevertheless be a sense in which truth could be an illusion, if we think that there are representations when in fact there aren't any. This is paradoxical territory, but for example there is a line of thought from Wittgenstein, articulated in Saul Kripke's Wittgenstein on Rules and Private Language, according to which our thoughts do not have determinate content. No determinate content, no determinate proposition, so no truth. If that were the situation, but we thought that there was truth here, we might (truly?) say that truth is an illusion.

Read another response by Richard Heck, Peter Lipton
Read another response about Knowledge, Truth