The ancient Greek philosopher Pythagoras, who gave his name to the Pythagorean theorum, also believed in the transmigration of souls from one creature to another; in other words, before you were born your soul might have been incarnated in Charles Dickens, and after you die, it might end up in a goat or a gnat. This philosophy led Pythagoras to disavow the eating of meat. After all, if a chicken can contain the soul of your great-grandpa, you don’t want to be tossing it (or him) into a crockpot. As a result of Pythagoras’s dietary philosophy, the word Pythagorean emerged in the late sixteenth century to denote a person who eschews the eating of flesh. That usage predates by more than two hundred years the appearance of vegetarian, which is first recorded in 1839. Still more recent is fruitarian, which appeared in 1893; such an individual will not eat anything if it involves killing. Thus, a fruitarian will not eat a carrot because doing so will kill the carrot; a fruitarian will, though, eat an orange or a nut, because the tree that produced them is not destroyed by consuming its fruit or seeds. Still more recent than either vegetarian or fruitarian is vegan, which was invented in 1944 as a name for a strict vegetarian, one that abstains not only from meat, but from eggs, fish, and dairy products. Small variations in dietary philosophy have, in recent years, spawned further terms, such as lacto-vegetarians (who will consume dairy products), ovo-vegetarians (who will consume eggs), pescatarians (vegetarians who will consume fish), and freegans. The latter term, formed by combining the word free with vegan, denotes a person who eats only food that has been discarded—for example, in dumpsters behind supermarkets or restaurants. Vegans do this as a political act, to protest the wastefulness of rampant consumerism. Less rigorous, and probably more fun, than any of these are flexitarians, individuals who are usually vegetarian but who will eat meat, eggs, and dairy products when a social situation warrants it. Flexitarian first appeared in English in 1992.