Ada Palmer explores how Renaissance readers, such as Machiavelli, Pomponio Leto, and Montaigne, actually ingested and disseminated Lucretius, and the ways in which this process of reading transformed modern thought. She uncovers humanist methods for reconciling Christian and pagan philosophy, and shows how ideas of emergent order and natural selection, so critical to our current thinking, became embedded in Europe’s intellectual landscape before the seventeenth century.