I really like this answer by Stephen Pinker responding to the issue of reason.



He talks about reason as the basis for acquiring knowledge, whether it be about the natural world (science), history, or ethics and morality.

Although I'd slightly disagree with him about what morality fundamentally is. He says it has to do with recognizing that others have needs and desires and projecting yourself onto them and realizing that your needs and wants are not the only ones in the universe, and realizing that others want to be treated in much the same way that you do. That's certainly a large part of it. But your morality also determines how you treat yourself, other non-sentient entities around you, and generally how you interact with the world. So his answer is a little anthrocentric, but I still like it very much.