A rationalist judges theories solely by their contents, not by their sources. But because contents are inseparable from meaning, he immediately faces the question of how to determine what a particular theory means. A theory can have an objective meaning only in a specific context. This dependence on context might seem to undermine the idea that a theory’s meaning can be objective. But the alternative ideas, that a theory either cannot have an objective meaning, or can preserve the same objective meaning across all contexts, are untenable. A theory exists only to solve a problem. Hence, a theory without its problem loses its meaning. Yet, considered together, a theory and its problem (i.e., its contents, given its context) are meaningful in their objective logical and explanatory relations to each other. And only creative and critical investigation of these objective relations—which is to say, only “rational thought”—can confirm that a theory solves its problem.