The author of the book C.S. Lewis' Dangerous Idea, is a philosophy professor by the name of Victor Reppert, who has apparently been hearing grumblings from his students about the value of studying philosophy. Everyone who teaches the subject (or any other subject, for that matter) has heard similar complaints. Philosophy students are often frustrated by the fact that philosophy seems to raise more questions than it answers and by the fact that few of the answers it does give are definitive. All of this is why I found Reppert's reply to his students very much on the mark.
He begins with this:
This is a response to some frustrations which a student expressed to me, and which are, I think, typical of a lot of people who are introduced to the subject. If you've taught philosophy for any length of time, you know where this student is coming from.
I know that philosophy, by its nature, can be frustrating, and it requires somewhat different skills than what you might be accustomed to using in other classes. I make no apologies for that; the discipline of philosophy is what it is.
There is a common conception when students come to philosophy classes that everything falls into two general categories, fact and opinion. If it is a matter of fact, we can settle it by some broadly scientific method. If it is a matter of opinion, then different people have different opinions, and we are all entitled to our opinions. Philosophical questions are all matters of opinion, and therefore there is something absurd and perhaps even offensive about grading a philosophy paper.
I think this neat division of everything into two boxes, fact and opinion, which we learned all the way back to fourth grade at least, is a distortion of the truth. Just because we cannot settle a question to everyone's satisfaction through a well-defined method doesn't mean that there can't be better or worse reasons for believing what we do, or that we shouldn't be aware of the reasons for and against what we believe. Whether it is worthwhile to spend time working through one's world-view and putting a lot of reflection into that, or whether there are other, more adequate uses for a person's time is not something I can answer for someone else.
If you've entertained the same musings as Reppert's student, or if you're a teacher, I encourage you to read the rest of his reply. It's quite good.
His book, by the way, is an excellent treatment of Lewis' argument in Miracles that the existence of human Reason is much better understood on the assumption that there's a God than it is on any naturalistic explanation.
RLC