This question touches on both relativity and quantum theory, but it is general enough that I think this is the place for it. I am aware that the Holy Grail of modern physics is a "Grand Unified Theory", or "Theory of Everything", that will combine general relativity and quantum theory into a cohesive whole. The fundamental issue, as I understand it, is trying to establish a model that successfully quantizes gravity. My questions are: Are general relativity and the Standard Model of quantum mechanics contradictory in some way? Do they make contrary predictions where we must assume that one or the other (or both theories) are false unless we accomplish a GUT? Is there some fundamental reason why we must believe gravity is quantized? Why couldn't we just accept at face value that gravity differs from the other 3 fundamental forces? Alternately - is the search for a GUT based on something more ephemeral? Is it really a search for theoretical "elegance" - conceptual "beauty"? Do we look for a GUT simply because it feels right that there should be one? My thanks in advance to anyone who can help clear this up for me.