Russell Shaw is right to father what he calls “New Natural Law theory” upon Germain Grisez (Letters, 7 June). There have been appeals to natural law since 416 BC, when the Athenians, according to Thucydides, used it to justify their massacre of the Melians. The connection of Grisez’s theory, which is tailor-made to fit the Magisterium’s teaching on contraception, with the permissive classical and Stoic theories, runs through the Roman lawyer Ulpian, who defines natural law as “what nature has taught all animals … the conjunction of male and female”. Aquinas does quote Ulpian’s definition in the Summa Theologiae. His condemnation of contraception, however, as a form of sex “against nature” (like intercourse with animals) comes in