“In manipulating their equations, mathematicians often get caught in a clutter of numbers, letters, and symbols. And for the same reasons you do around the house, they periodically take time to tidy up—so they’re not forever stepping over mounds of mathematical debris, and so any attractive qualities of their mathematical habitat are shown off to best advantage. “Grouping like terms” is one form housecleaning takes; you cluster mathematical entities in their appropriate categories. You place dirty clothes in the laundry bin, freshly laundered napkins in the linen drawer, cereal back in the pantry. You put things where they belong.”
