When I was a young academic, I felt a certain obligation to make myself aware of philosophy. I started with the preSocratics and worked my way, in no particular order, to the postModernists. It was a long, hard slog, and except perhaps for David Hume I can't say that I'm better off because of it. The Greeks stated the questions succinctly: What is the good? What is beauty? What is truth? Shelves and shelves of tomes follow. Two-and-a-half millennia after Socrates, philosophers are still rearranging the furniture in the House of Intellect.
What is the good? Do unto others as you would have them do unto you. Altruism almost certainly has evolutionary roots. Let us repair to science for the origin of the Golden Rule.
What is beauty? Beauty is what we find beautiful. What we find beautiful also has likely been determined by natural selection.
What is truth? Ah, now that's the truly interesting question. Perhaps we will never know. For the time being, the best answers come not from the philosophers, who like spiders spin webs of their own substance, but from the intellectual successors of the mathematical empiricists of Alexandria, the worker bees in the hive of science who make honey from nectar -- not Truth with a capital T, to be sure, but the best sort of truth we are presently able to obtain. Francis Bacon (who supplied my spider/bee metaphor) put it this way: truth "is extracted...not only out of the secret closets of the mind, but out of the very entrails of Nature." We call it, loosely, the scientific method. It involves the "closets of the mind," certainly; no way to avoid that. But it also involves interrogating nature in a way that forces a maximally unambiguous response, which means quantitative reasoning, quantitative measurement, and reproducible experiment. As Hume told us, reason alone is a dead-end road on the journey to truth. The anticipation of nature is a fraud.
But that hasn't stopped the Bs (philosophy) from expanding as rapidly as any other category of books in the library. What we get is a few books by Kant, say, followed by a half-dozen shelves purporting to tell us what Kant was saying. Ditto Nietzsche. Ditto Derrida. Etc. A cottage industry for academics. As I enter my Golden Years, my pursuit of answers to the three big questions takes me mostly to the Ps (literature) and the Qs (science). In my humble view, all of those laden shelves of philosophy can be reduced to a few words: Be good, leave the world a more beautiful place than you found it, be skeptical of claims for absolute Truth.