Lucretius' purpose is to correct ignorance and to give the knowledge necessary for managing one's sex life rationally. He distinguishes between pleasure and conception as goals of copulation; both are legitimate, but require different approaches. He recommends casual sex as a way of releasing sexual tension without becoming obsessed with a single object of desire; a "streetwalking Venus"—a common prostitute—should be used as a surrogate. Sex without passionate attachment produces a superior form of pleasure free of uncertainty, frenzy, and mental disturbance. Lucretius calls this form of sexual pleasure "venus", in contrast to "amor", passionate love. The best sex is that of happy animals, or of gods. Lucretius combines an Epicurean wariness of sex as a threat to peace of mind with the Roman cultural value placed on sexuality as an aspect of marriage and family life, pictured as an Epicurean man in a tranquil and friendly marriage with a good but homely woman, beauty being a disquieting prompt to excessive desire. Lucretius reacts against the Roman tendency to display sex ostentatiously, as in erotic art, and rejects the aggressive, "Priapic" model of sexuality spurred by visual stimulus.