Philosophy and literature are artifacts of human culture--that is, they can only be understood in the context of human culture and society. In contrast, scientific facts like the mass of the proton are exactly the same everywhere in the universe (or so we presume).

That doesn't mean that philosophy and literature--and art, and music, and film, and all the other "humanities"--aren't part of human knowledge. They are, and they can have profound impacts on human society, which in turn, has significant impacts on the physical world on the Earth's surface.

When humans interact with the physical environment, we use heuristics to model the physical realities of nature in a usable way. Think of catching a baseball; we have an internal model of the Earth's gravitational field that allows us to predict the path of the ball, and place our hand in just the right spot to catch it.

When we interact with other humans we use heuristics too. These are affected by the cultural experiences we have, which include art, stories, movies, etc. When we evaluate a politician, for example, we are applying the heuristics developed by hearing, seeing, and telling stories. We think one guy looks creepy, and another trustworthy...why? Because of what we've learned about humans so far, and a lot of that comes from literature, art, philosophy, etc.