 In the context of thermodynamic systems containing black holes, one can easily construct apparent violations of both the ordinary laws of thermodynamics and the laws of black holes if one applies these laws independently of each other. So, for example, if a black hole emits radiation through the Hawking effect, then it will lose mass—in apparent violation of the classical Second Law of black hole mechanics. Likewise, as Bekenstein argued, we could violate the ordinary Second Law of thermodynamics simply by dumping matter with high entropy into a black hole: for then the outside of the black hole, a causally isolated system, spontaneously decreases in entropy. The price of dropping matter into the black hole, however, is that its event horizon will increase in size. Likewise, the price of allowing the event horizon to shrink by giving off Hawking radiation is that the entropy of external matter fields will increase. This suggests that we should formulate a combination of the two laws that stipulates that the sum of a black hole's area and the entropy of external systems can never decrease. This is the Generalized Second Law of thermodynamics (Bekenstein 1972, 1973, 1974). 