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 … - Julian Baggini

There is an irony here. On the one hand, all of these mistakes point to hubris, a belief that human reason is more powerful than it really is. But on the other, all these mistakes implicitly acknowledge how limited the power of reason is, because they require us to simplify our conception of the world in order to make it tractable to reason. It is as though in order to preserve the illusion that human reason is mighty, we have to rig its challenges to make them easier to overcome.

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.

I think intellectual honesty demands that philosophers accept this all-pervading normativity more openly. Apart from anything else, this helps explain why philosophy matters. We are not just disputing what is true or false, we are arguing about what we ought to think. Persuasion is not the same as rational argument but every rational argument is and ought to be an exercise in persuasion. Ideas only matter because we ought to believe the right ones. Reason in philosophy is therefore in a sense never disinterested.