It is often difficult to know about one's own era which philosophers in it will be remembered as the most important ones, but I think it is already clear that John Rawls is the greatest moral philosopher of the twentieth century.

In any matter of moral importance, our first task, before we plunge ahead and decide what to do, is to figure out what we ought to do.

Kant's aim was to develop a religion within the boundaries of mere reason (that is, reason unaided by special empirical revelation) and then to ask about existing ecclesiastical faith (especially about Christianity, and the Lutheran Christianity of his time and place) how this revealed faith must be interpreted if it is to be reconciled with reason, and even seen as a wider (though morally optional) extension of a religion of reason.

When people think that moral problems can be solved by some simple strategy of calculation, that sets them up for ghastly overreaching. They think they can turn everything into a "science" the way mechanics was turned into a science in the seventeeth century. They want to turn everything over to technocrats and social engineers. They become shortsighted or simplistic about their ends, and they disastrously overestimate their ability to acquire the information they need to make the needed calculations.

Empiricist philosophy always tends to be anti-philosophy (and is often proud of it).

Kant does not think there is anything wrong with being beneficent from sympathy. He thinks we have a duty to cultivate sympathetic feelings by participating in the situations of others and acquiring an understanding of them. He thinks we also have a duty to make ourselves into the kind of person for whom the recognition that something is our duty would be a sufficient incentive to do it (if no other incentives were available to us). That's what he means by "the duty to act from the motive of duty".

Consequentialist theories begin with a very simple and undoubtedly valid point: Every action aims at a future end, and is seen as a means to it.