I've always thought that the greatest use of such a spell (such as know alignement, detect evil or true sight) would be to discern one's own alignment. I mean, wouldn't it be strange to think of yourself as mostly lawful and good only to cast the spell and come to the horrific realization that you are infact chaotic evil? Imagine casting it on yourself and thinking: "But I'm not evil, just pragmatic. I folow most of the laws, the one's that matter at least. I'm not that bad am I? I mean I did kill that one guy, but come on, that rat-bastard *deserved* to die; he *needed* to die. It was like a public service. If I didn't do it, who would have? I donated a silver to that beggar last week! Doesn't charity count for something? How can I be EVIL?!?"