In Plato's Phaedrus, Socrates famously described the virtues of two complementary ways of looking at the world. The first entailed "seeing together things that are scattered about everywhere and collecting them into one kind," while the second was the skill "to cut up each kind according to its species along its natural joints, and to try not to splinter any part, as a bad butcher might do." In a similar sentiment, Darwin wrote in 1857, "It is good to have hair-splitters and lumpers." How have naturalists and biologists perceived similarities and differences in the living world? How have they divided nature into kinds and individuals? How have they distinguished between parts and wholes? This course explores these and related questions through the history of biology, from Renaissance-era natural histories through present-day studies of molecular evolution. Other topics covered will include histories of comparative anatomy, immunology, mutations, commensalism, cloning, and biodiversity conservation.