Why Are You Taking Philosophy?

What if a friend asked, "Why are you studying philosophy? It is an abstract useless subject"? How would I respond? I would ask my friend a series of questions in the attempt to reveal whether he has asked this questions based on assumptions or if he has reasoned out the practical uses of philosophy for himself and came to the conclusion that philosophy, "is an abstract useless subject". My friend's question has one main hidden assumption that I would attack: what is abstract is useless. To further illustrate my response to this hypothetical question I would like to create a hypothetical dialog in which I will do as I have said and attack my friend's assumptions through asking a series of my own questions. For the sake of this dialog my friends name will be David and I will be James.
David: Why are you studying philosophy? It is an abstract useless subject.
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