Institutional differentiation has frequently been an object of interest in higher education policymaking in Ontario. Occasionally this interest has motivated policy actions intended to increase differentiation, but more often government policy has aimed at limiting institutional differentiation -- or it has had that effect by default. The focus of this article is on the "idea" of differentiation as revealed, or suggested, in the policy discourse on higher education. In looking at discussions of higher education policy in Ontario over a long period of time, the author highlights two general features of those discussions: (1) dimensions of institutional differentiation of interest; and (2) tension between differentiation and geographic accessibility.