 What does all this have to do with black holes? At first glance, nothing. On deeper reflection, however, quite a lot. Hawking's Area Theorem, that black holes never decrease in size and can only increase, is time asymmetric in the same way as the behavior of ordinary physical systems governed by the Second Law. This, recall, was the basis for the postulation of the Generalized Second Law, based on the idea that black holes themselves possess entropy, itself one of the motivating reasons that have led physicists to hypothesize that the gravitational field in general, not just black holes, possess an intrinsic entropy  (section 5.5),  as Penrose (1979) hypothesized. Indeed Penrose did far more than just argue that the gravitational field itself possesses a generalized entropy. He also proposed what has come to be known as the Conformal Curvature Hypothesis, which states that the gravitational and cosmological arrows of time are driven, if not determined, by this generalized gravitational entropy. 