This paper examines the nature of rational choice in strategic games. Although there
are many reasons why an agent might select a Nash equilibrium strategy in a particular
game, rationality alone does not require him to do so. A natural extension of widely
accepted axioms for rational choice under uncertainty to strategic environments generates
an alternative class of strategies, labelled "rationalizable." It is argued that
no rationalizable strategy can be discarded on the basis of rationality alone, and
that all rationally justifiable strategies are members of the rationalizable set.
The properties of rationalizable strategies are studied, and refinements are considered.