Beginning with a brief sketch of the derivation of Hawking's theorem of
horizon area increase, based on the Raychaudhuri equation, we go on to discuss
the issue as to whether generic black holes, undergoing Hawking radiation, can
ever remain in stable thermal equilibrium with that radiation. We derive a
universal criterion for such a stability, which relates the black hole mass and
microcanonical entropy, both of which are well-defined within the context of
the Isolated Horizon, and in principle calculable within Loop Quantum Gravity.
The criterion is argued to hold even when thermal fluctuations of electric
charge are considered, within a {\it grand} canonical ensemble.Comment: Latex2e, 13 pages, 2 eps figures. Contribution to the volume to be
published by the Indian Association for the Cultivation of Science, Kolkata,
India in revered memory of Prof. A. K. Raychaudhur
