What Did the Romans Know? is a brilliant achievement. Equally historical and philosophical, Lehoux's book is simultaneously sophisticated and accessible. Virtually every page presents provocative and well-grounded insights that reshape what we thought we knew about the Romans and their interconnected world of nature, law, and religion. It is required reading for historians and philosophers, classicists, and anyone interested in antiquity and the bases of human knowledge about the natural world. --Lawrence M. Principe, Johns Hopkins University