  Nonperturbative terms in the free energy of Chern-Simons gauge theory play a
key role in its duality to the closed topological string. We show that these
terms are reproduced by performing a double scaling limit near the point where
the perturbation expansion diverges. This leads to a derivation of closed
string theory from this large-N gauge theory along the lines of noncritical
string theories. We comment on the possible relevance of this observation to
the derivation of superpotentials of asymptotically free gauge theories and its
relation to infrared renormalons.
