The importance of the concept of intelligibility is closely related to the fact that the most basic distinction of all embedded in our discourse and our practice in this area is that between human beings and other beings. Human beings can be held to account for that of which they are the authors; other beings cannot. To identify an occurrence as an action is in the paradigmatic instances to identify it under a type of description which enables us to see that occurrence as flowing intelligibly from a human agent’s intentions, motives, passions and purposes. It is therefore to understand an action as something for which someone is accountable, about which it is always appropriate to ask the agent for an intelligible account. When an occurrence is apparently the intended action of a human agent, but nonetheless we cannot identify it, we are both intellectually and practically baffled. We do not know how to respond; we do not know how to explain; we do not even know how to characterize minimally as an intelligible action; our distinction between the humanly accountable and the merely natural seems to have broken down. And this kind of bafflement does indeed occur in a number of different kinds of situation; when we enter alien cultures or even alien social structures within our own culture, in our encounters with certain types of neurotic or psychotic patient (it is indeed the unintelligibility of such patients’ actions that leads to their being treated as patients; actions unintelligible to the agent as well as to everyone else are understood–rightly–as a kind of suffering), but also in everyday situations.
–Alasdair MacIntyre, 1984