"Truth is such integral part of our intellectual world that it’s hard to define without being trivial or totally obscure. Aristotle put it this way: 'To say of what is that it is not, or of what is not that it is, is false; while to say of what is that it is, or of what is not that it is not, is true.'

To realize how slippery the idea is, notice that none of those formulations gives a definition of truth. They all tell us when something is true, but not what it means for something to be true."

— Why Sane People Believe Crazy Things: How Belief Can Help or Hurt Social Peace