One of the interesting things about the ancient Greeks is that they really didn't have our conception of individual rights. They didn't have our conception of all lives matters. And it was really was true for them, that certain lives matter a lot more than others. It didn't dawn on them that all lives, although different, can be lives of equal mattering. And that is actually something a huge ethical lesson.

If there is such a thing as philosophical progress, then why - unlike scientific progress - is it so invisible? Philosophical progress is invisible because it is incorporated into our points of view. What was torturously secured by complex argument comes widely shared intuition, so obvious that we forget its provenance.

Plato conceived of philosophy as necessarily gregarious rather than solitary. The exposure of presumptions is best done in company, the more argumentative the better.

In fact, it’s the very impersonality of impersonal knowledge that renders such knowledge the most ethically potent of all.

And then there is Pythagoras. The legend is that the founder of theoretical mathematics was so outraged when one of his students, the haplessly gifted Hippasus, discovered irrational numbers that he sent the poor fellow out on a raft to drown, initiating a venerable tradition of professors mistreating their graduate students.

And what is it, according to Plato, that philosophy is supposed to do? Nothing less than to render violence to our sense of ourselves and our world, our sense of ourselves in the world.

We may not need God to tell us where the world came from, but we need God to be able to live moral lives and for there to be morality in the first place.