Only our most intimate friends know our deepest flaws, and in the same way the greatest skeptics about reason should be those who seek to defend it. … - Julian Baggini

This point is, in essence, the most important and overlooked one regarding the rationality of ethics. The traditional dispute between Kantians and sentimentalists rests on an assumption that to be rational, morality must be grounded on a priori principles of disinterested reason. This is false. If we understand what rationality means in an appropriately catholic way, we see that it it is a matter of providing reasons for belief and that the sources of these reasons are not confined to a priori principles of logical or scientific facts. Once we accept that, we can see that although the Kantian project of founding ethics on pure reason is doomed, reason is still at the very heart of morality.

Philosophers understandably focus on the nature of reason itself. However, in order for reason to flourish, it needs to be practised in the right environment. And that is sadly often lacking in the very places where reason is held in the highest esteem.

In this way we can see that political reason is as much – if not more – bottom-up than top-down. Rationality requires attending to objective reasons for belief and many of the most important such reasons are provided by what we observe in the world. Indeed, what we observe is of primary importance: there is no hope of understanding justice, for example, if we attempt to do so purely by examining the concept without any reference at all to what we perceive to be just or unjust in the world.