  We discuss some general properties of quantum gravity in De Sitter space. It
has been argued that the Hilbert space is of finite dimension. This suggests a
macroscopic argument that General Relativity cannot be quantized -- unless it
is embedded in a more precise theory that determines the value of the
cosmological constant. We give a definition of the quantum Hilbert space using
the asymptotic behavior in the past and future, without requiring detailed
microscopic knowledge. We discuss the difficulties in defining any precisely
calculable or measurable observables in an asymptotically de Sitter spacetime,
and explore some meta-observables that appear to make mathematical sense but
cannot be measured by an observer who lives in the spacetime. This article is
an expanded version of a lecture at Strings 2001 in Mumbai.
