Multiple knowledges are available for utilisation in policy choice. The rank ordering of knowledges for use in decisionmaking is thus a fundamental predecision. This article shows how this predecision necessarily constrains the processes associated with a politics of ideas, using cases from American international commodity policy. Even when the supposed preconditions of this sort of politics are present, policy change did not occur when the proposed ideas arose from a knowledge accorded secondary status in policymaking circles. Several implications are discussed for the influence and the study of ideational politics. Ultimately, the politics of ideas, so often portrayed through cases of innovation, may be quite conservative, contained by knowledge hierarchies which reflect prior political circumstances.