But we can now more fruitfully approach Prichard’s position in another way...

But we can now more fruitfully approach Prichard’s position in another way, and exhibit its historical roots.

If we do so, we shall see a gradual attenuation of the concept of duty and of kindred concepts, in which there is a progress from a notion of a duty as consisting in the requirement to fulfill a specific role, the fulfillment of which serves a purpose which is entirely intelligible as the expression of normal human desires (consider the duties of a father, seaman, or doctor as examples); the next step is perhaps the concept of duty as something to be done by the individual whatever his private desires; finally, we reach the concept of duty as divorced from desire altogether.

If we could not explain Prichard’s concept of duty historically, I think we should be very much in the position of anthropologists who come across a new and incomprehensible word, such as, for example, tabu, a word which is puzzling because it appears not simply to mean “prohibited” but to give a reason for the prohibition, without its being clear what reason.

So when someone like Prichard says it is our “duty” to do something, he does not just tell us to do it, as though he uttered an injunction “Do that,” but he appears to give us a reason. Consequently, just as we may ask of Polynesians why we should refrain from doing something because it is tabu, so we shall want to ask Prichard why we should do something because it is our duty.

And in each case the answer will be similar, and similarly incomprehensible: “Because it is tabu,” “Because it is your duty.” The lack of connection with other aims, purposes, and desires produces in the end unintelligibility. Yet the concept which Prichard elucidates is one in common use. “‘Why ought I to do that?’ ‘You just ought’” is not uncommon as a form of moral dialogue in modern society.

Thus the philosophical elucidation raises interesting problems about the role of the concept in our social life. But rather than pursuing these at this stage, we must instead return to the Greeks. The crucial point for the immediate discussion is that it may now be clearer why we could not use the moral words which express the modern concept of duty in translating Greek moral words; for these retain the connection with the vocabulary of desire in terms of which they can be made intelligible.

The function of evaluative terms in Greek is, then, to grade different possibilities of conduct in terms of our desires; but in terms of which of our desires?