  We argue that the topological string partition function, which has been known
to correspond to a wave-function, can be interpreted as an exact
``wave-function of the universe'' in the mini-superspace sector of physical
superstring theory. This realizes the idea of Hartle and Hawking in the context
of string theory, including all loop quantum corrections. The mini-superspace
approximation is justified as an exact description of BPS quantities. Moreover
this proposal leads to a conceptual explanation of the recent observation that
the black hole entropy is the square of the topological string wave-function.
This wave-function can be interpreted in the context of flux compactification
of all spatial dimensions as providing a physical probability distribution on
the moduli space of string compactification. Euclidean time is realized
holographically in this setup.
