The fourth book of Lucretius' "De rerum natura" provides one of the most extended passages on human sexuality in Latin literature. Yeats, describing the translation by Dryden, called it "the finest description of sexual intercourse ever written." Lucretius was the contemporary of Catullus and Cicero in the mid-1st century BC. His didactic poem "De rerum natura" is a presentation of Epicurean philosophy within the Ennian tradition of Latin poetry. Epicureanism is both materialist and hedonic. The highest good is pleasure, defined as the absence of physical pain and emotional distress. The Epicurean seeks to gratify his desires with the least expenditure of passion and effort. Desires are ranked as those that are both natural and necessary, such as hunger and thirst; those that are natural but unnecessary, such as sex; and those that are neither natural nor necessary, including the desire to rule over others and glorify oneself. It is within this context that Lucretius presents his analysis of love and sexual desire, which counters the erotic ethos of Catullus and influenced the love poets of the Augustan period.