Abstract:

The area law for black hole entropy makes sense if the
entropy resides on the horizon (with about one bit of
information per unit area).  What these bits of information
really represent depends on the deep structure of spacetime.
The two main tasks, then, are: to identify (and count) the
``bits'' and to explain why the total entropy increases.  I will
maintain that the finiteness of the entropy teaches us that a
discrete structure such as a causal set underlies spacetime and
the teleological character of the horizon implies that quantum
gravity requires a spacetime formulation (as opposed to a
Hamiltonian or ``canonical'' one).