  We show that the canonical ensemble in any of the six supersymmetric string
theories, type IIA and IIB, type IB and type I', or heterotic E_8 x E_8 and
Spin(32)/Z_2, exhibits a strong version of holography: the growth of the number
of degrees of freedom in the free energy at high temperatures is identical to
that in a two-dimensional quantum field theory. We clarify the precise nature
of the thermal duality phase transition in each case, confirming that it lies
within the Kosterlitz-Thouless universality class. We show that, in the
presence of Dbranes, and a consequent Yang-Mills gauge sector, the thermal
ensemble of type II strings is infrared stable, with neither tachyons nor
massless scalar tadpoles. Supersymmetry remains unbroken in the oriented closed
string sector, but is broken by thermal effects in the full unoriented open and
closed type I string theory. We identify an order parameter for an unusual
phase transition in the worldvolume gauge theory signalled by the short
distance behavior of the pair correlator of timelike Wilson loops. Note Added
(Sep 2005).
