[math-fun] Is mathematical truth "real" ?

If this common discussion subject among mathematicians has come up in math-fun previously, it must have been a while ago: Is mathematical truth real? I was reminded of this question when I happened to sit next to an esteemed molecular biologist who has strong opinions on the matter: He thinks math is "all in the brain" of humans who think about it. I could not convince him that math has any kind of independent existence — though I certainly believe it myself. What do other think about this? I would say that mathematical truth is *at least* as real of a thing as physical truth. —Dan