PREFACE -- It is now some time since philosophers stopped being sages who told us about Ultimate Reality or The Meaning of Life. Nowadays, they do not even tell us what moral principles to adopt; and modern analytic philosophy is usually regarded as an expertise reserved for professional philosophers. Consequently, the attempt to apply it to sexual morality will inevitably seem unreal and even absurd to some: while to others -- since it is applied in a highly diluted form -- it is bound to seem unscholarly. -- However, this is an age in which very few educated people will accept any authority uncritically. Even if philosophers did now pose as sages, hardly anyone would listen to them: and quite right too. The philosopher is not able, and should not try, to take the weight of moral decision off our shoulders. What he can do is to help us make our own moral decisions for ourselves.