 The question of whether we should be troubled by this possible violation of the Generalized Second Law touches on several issues in the foundations of physics. The status of the ordinary Second Law is itself a thorny philosophical puzzle, quite apart from the issue of black holes. Many physicists and philosophers deny that the ordinary Second Law holds universally, so one might question whether we should insist on its validity in the presence of black holes. On the other hand, the Second Law clearly captures some significant feature of our world, and the analogy between black holes and thermodynamics seems too rich to be thrown out without a fight. Indeed, the Generalized Second Law is the only known physical law that unites the fields of general relativity, quantum mechanics, and thermodynamics. As such, it seems currently to be the most promising window we have into the most fundamental structures of the physical world (for discussion of which, see  section 6.3  below). 