例子: Contrast the periodic table of the elements – a system of chemical classification positing a hundred chemical categories (hydrogen, carbon, gold, barium, etc.) – with some random, arbitrary grouping of objects: all the things in your bedroom count as one chemical element, all the things in your kitchen count as another, and so on. Chemists at least think that what they are doing with the periodic table is carving things up according to objective distinctions that exist in the world prior to our taking an interest in them, whereas the alternative system of chemical classification just described would be doing no such thing.