In the minds of most philosophers and historians of philosophy, the idea of the summum bonum (highest good) comes embedded in a question: what is the summum bonum? The idea seems entertainable to the extent that the question seems real. For the question to seem real at least two conditions must hold. First, it must seem as if some answers are objectively better than others. Secondly, it must not seem straight off obvious what the right or best answer to the question should be. But there is also, presumably, a third desideratum, namely agreement, implicit or explicit, on the second order question of what is meant by regarding X as the highest good, whatever X may be. This second order question is my subject here.

Let me approach by observing that the notion of ‘the highest good’ is marginal for modern ethical theories, although arguably it is the determinative concept of every ancient such system. We have all learnt to classify the antique examples in terms of the highest good according to each. Still, no surprise if after two millennia very different themes are now to the fore. But emergence of new claimants for attention does not really explain why the once supremely important notion of the highest good has pretty well dropped out of sight.

I shall begin by identifying an influence which I believe helps explain why the notion has been in eclipse, anyway during the last century and a half of ethical philosophising. This influence, I shall maintain, incorporates a modern misunderstanding of what, historically, it means to say of something that it is the highest good.