What does "physical" mean to philosophers?

Question

A childish question (literally) - My 8 year old asked me this morning: "Dad, what does 'physical' mean?" - and I found myself at loss for an ordinary language answer. Every answer I could come up with ended up sounding like a definition of empiricism: "physical things are those things that can be observed", "physical means something that can be measured", "whatever can be verified and tested", etc.... Claiming that things that are physical are those things which are material or things that are described by physics seems circular.

Answer 1

Colloquially, what philosophers (mostly, in philosophy of mind) mean by "physicalism" does seem to be "what can be described by the physical sciences" at large. So if someone is stating that they're a physicalist in that domain, they tend to mean that the brain can only be understood as something ultimately understandable in that domain. This is juxtaposed against mind-body dualism, wherein the mind is separate from the brain, often taking a supernatural quality.

In other contexts, what physicalism seems to mean is "the view that a certain (or all) domains can be made intelligible with the physical sciences", though it is less clear how neatly this maps onto other fields.