 In the remainder of this section, we will review the issues raised by the Generalized Second Law that bear on those puzzles and questions, namely that: contrary to the case in classical thermodynamics, the Generalized Second Law admits not only of proof, but of many kinds of proof  (Section 5.4.1);  several different physically plausible mechanisms have been proposed that seem to violate the Generalized Second Law  (Section 5.4.2)  under relatively benign conditions; the Generalized Second Law seems to allow for the possibility of formulating and proving the existence of a universal bound on the amount of entropy any physical system can have, along with a related constellation of ideas known as ‘holography’  (Section 5.4.3);  and, contrary to the Second Law of classical thermodynamics, the Generalized Second Law seems to imply novel and deep propositions of interest in their own right  (Section 5.4.4).  The possible connection of the Generalized Second Law to the arrow of time is discussed in  Section 7  below. 