If you’ve been intrigued (but possibly unconvinced) by my recent arguments about induction and the nature of scientific proof, go read Sean Carroll’s riff on the distinction between belief and proof in science. When we’re discussing the existence of quarks (or superstings), this may seem a literally academic argument, but these distinctions surface in ongoing public discussions with real policy repercussions. Are humans responsible for climate change? Are present-day animals (including humans) the result of billions of years of evolution? We can’t prove either of these things — to use the language of the deniers, they are “just theories”. But theories are all we ever have about the world.