" This is why one hears scientists talking about the “theory” of evolution. It is not an observed fact; rather, it is a conclusion that is supported by all the facts observed so far, but one can never be absolutely sure because one can never see the whole universe at once, and because of the provisional nature of inductive reasoning, scientists hold out the possibility, no matter how small, that it could be invalidated. Science thus demands intellectual honesty, and a scientific conclusion will always contain a provisional statement: All observed swans are white; therefore, all swans are probably white. "

― Shawn Lawrence Otto , The War on Science: Who's Waging It, Why It Matters, What We Can Do About It