The article first (i) gives an exegesis of the famous passage in the Republic, 505d11-506a2. Attention is drawn to the fact that the principle that every soul does everything for the Good (panta prattei) can be translated in two ways: Every soul does everything for the sake of the Good, or goes to all lengths for the sake of the Good. Depending on the different translations, we have a different picture of the Platonic Socrates in the Republic, an intellectualistic Socrates for whom pure irrational desires do not exist, or a Socrates who also accepts irrational desires. The article favours the first picture. Then it (ii) attempts to show that we can elucidate two dark points in the principle that the Good is that for which every soul does everything, with the help of Aquinas’s distinction between an actio hominis and an actio humana. Finally, the article (iii) outlines three substantive answers to the question “What is the Good?” – the henological, the perfectionist and the structuralist – and shows that these three answers lead into a trilemma. Instead of advancing a new answer, the article suggests an uncontroversial formal starting point for an answer to this question.