I had a nice discussion last night at dinner with a philosophy graduate student. I mentioned that condensed matter physics deals with finding emergent phenomena in complex systems. The philosophy grad student lit up and told me that "emergent phenomena" are also a hot topic in philosophy. Apparently, some philosophers think that values are an emergent phenomenon. Then we debated a bit about whether values are "objective" (an absolute truth like numbers) or "subjective" (dependent on the viewer's opinion).
Personally, I think the categories of objective and subjective are too narrow. There should be some kind of in-between category which values would fall under. I don't think there are any absolute values. There is always an exception to a rule. For example, one of the ten commandments is "thou shalt not kill." But what if I'm being attacked with no provocation? Of course, as C.S. Lewis would say (see his book Mere Christianity), it seems like there are some guiding moral principles that most people can agree on. So values are not subjective either.
My roommate was really interested in how to psychologically deal with the idea that we might all be "brains in a vat." The philosophy graduate student made two good points. First, the question of being a brain in a vat is by definition unknowable. So it seems silly to worry about it. Second, reality should be taken in context. Maybe we are living in a Matrix-like environment and our bodies are plugged into a computer. But that doesn't make our perceptions false. In the context that we perceive, our hands are real, the table when I tap it is real. The idea of context is very natural to a physicist. I don't go around telling people that quantum mechanics is true (in the absolute sense). But when we study phenomena on the scale of atoms, then quantum mechanics is the appropriate lenses to understand these phenomena.
I have mixed feelings about philosophy. On the surface, it seems like a fascinating topic. But at the end of the day, when you twist and turn your brain, you don't feel like you've learned anything. I think philosophy focuses too much on finding absolute truth and thus sometimes gets sidetracked from the practical matters of living -- which is the reason why I'm interested in philosophy in the first place.