It has always seemed to me that philosophy - and much theology as well - does not ask these question often enough. The art of philosophy appears to be to notice something about the world and then make up some sort of system of definitions and thinking based on a couple of observations, and then talk and act as if that system is reality. There is little enough attempt to recognize that there are some observations backing up the system of thought; there is almost never any attempt at all to recognize or determine when the system of thinking might not apply or whether they have any real meaning or (non-propagandist) usefulness at all.
To sum up: "Philosophy is all made-up."
So I'm going along today, and I happen to be reading through a bunch of articles by some mathematician named Devlin, because I'm homeschooling the kids and I think a lot of what he says might have some relevance to how I go about teaching them math. And I happen across him saying something about how mathematicians learn math the way that they learn chess, and I instantly think that that's exactly how we learn philosophy too. Here's the quote.
Rather, a mathematician (at least me and others I've asked) learns new math the way people learn to play chess. We first learn the rules of chess. Those rules don't relate to anything in our everyday experience. They don't make sense. They are just the rules of chess. To play chess, you don't have to understand the rules or know where they came from or what they "mean". You simply have to follow them. In our first few attempts at playing chess, we follow the rules blindly, without any insight or understanding what we are doing. And, unless we are playing another beginner, we get beat. But then, after we've played a few games, the rules begin to make sense to us - we start to understand them. Not in terms of anything in the real world or in our prior experience, but in terms of the game itself. Eventually, after we have played many games, the rules are forgotten. We just play chess. And it really does make sense to us. The moves do have meaning (in terms of the game). But this is not a process of constructing a metaphor. Rather it is one of cognitive bootstrapping (my term), where we make use of the fact that, through conscious effort, the brain can learn to follow arbitrary and meaningless rules, and then, after our brain has sufficient experience working with those rules, it starts to make sense of them and they acquire meaning for us. (At least it does if those rules are formulated and put together in a way that has a structure that enables this.)
Arbitrary and meaningless rules, which once we have been exposed to them enough (say through a philosophy class), begin to seem sensible. Yep, that's philosophy all right. How does Paul put it? Ah yes, Romans 1:22 - "Believing themselves wise, they became foolish".
(Note: I am not actually ranting against ALL philosophy, just what I see as a very common current within it. I have no objection to philosophy that asks itself whether its thoughts are real, so to speak.)