  In previous work it was shown that, in accord with the Brandenberger-Vafa
mechanism, three is the maximum number of spatial dimensions that can grow
large cosmologically from an initial thermal fluctuation. Here we complement
that work by considering the possibility of successive fluctuations. Suppose an
initial fluctuation causes at least one dimension to grow, and suppose
successive fluctuations occur on timescales of order alpha'^{1/2}. If the
string coupling is sufficiently large, we show that such fluctuations are
likely to push a three-dimensional subspace to large volume where winding modes
annihilate. In this setting three is the preferred number of large dimensions.
Although encouraging, a more careful study of the dynamics and statistics of
fluctuations is needed to assess the likelihood of our assumptions.
