William Charlton (Letters, 24 May) repeats the assertion, often made by persons who reject the Church’s teaching on contraception, that there is no rational argument in support of the teaching except the tradition of the Church. But this is not the case. The assertion overlooks the argument against contraception put forward by the New Natural Law theory.The New Natural Law argument was first advanced by the American ethicist and moral theologian Germain Grisez in his 1965 book Contraception and the Natural Law and since then has been developed in numerous published works by Grisez, John Finnis and others. It is not the argument of St John Paul II’s Theology of the Body but something quite different. Many people find it highly persuasive. Those who do not do nothing to advance