While epistemology is concerned with what we ought to believe and how we ought to reason, Ethics is concerned with what we ought to do, how we ought to live, and how we ought to organize our communities. Sadly, it comes as a surprise to many new philosophy students that you can reason about such things. Religiously inspired views about morality often take right and wrong to be simply a matter of what is commanded by a divine being. Moral Relativism, perhaps the most popular opinion among people who have rejected faith, simply substitutes the commands of society for the commands of God. Commands are simply to be obeyed, they are not to be inquired into, assessed for reasonableness, or tested against the evidence. Thinking of morality in terms of whose commands are authoritative leaves no room for rational inquiry into how we ought to live, how we ought to treat others, or how we ought to structure our communities. Philosophy, on the other hand, takes seriously the possibility of rational inquiry into these matters. If philosophy has not succeeded in coming up with absolutely certain and definitive answer in ethics, this is in part because philosophers take the answers to moral questions to be things we need to discover, not simply matters of somebody’s say so. The long and difficult history of science should give us some humble recognition of how difficult and frustrating careful inquiry and investigation can be. So we don’t know for certain what the laws of morality are. We also don’t have a unified field theory in physics. Why expect morality to be any easier?
So we might think of metaphysics as concerned with “What is it?” questions, epistemology as concerned with “How do we know?” questions, and ethics as concerned with “What should we do about it?” questions. Many interesting lines of inquiry cut across these three kinds ofquestions. The philosophy of science, for instance, is concerned with metaphysical issues about what science is, but also with epistemological questions about how we can know scientific truths. The philosophy of love is similarly concerned with metaphysical questions about what love is. But it also concerned with questions about the value of love that are more ethical in character.
Assorted tangled vines of inquiry branch off from the three major trunks of philosophy, intermingle between them, and ultimately with scientific issues as well. The notion that some branches of human inquiry can proceed entirely independent of others ultimately becomes difficult to sustain. The scientist who neglects philosophy runs the same risk of ignorance as the philosopher who neglects science.