Perhaps the most important element of James Buchanan’s contribution to constitutional economics is his differentiation between pre- and post-constitutional levels of decision-making. At first glance, a tension may appear between those two levels of analysis. In one, the rules by which we live are up for debate, allowing us to exercise our creative and imaginative capabilities in constitutional construction. In the other, the rules are viewed as fixed, and we are left simply to treat them as constraints. This paper explores three key elements of Buchanan’s thought that allow him to navigate successfully between the two levels. The first is the importance of “the relatively absolute absolute”, a concept learned from his mentor, Frank Knight. The second is Buchanan’s approach to “truth judgments” in politics, and their status in our political discussions. Third, we draw on Buchanan’s insights in his 1959 paper “Positive Economics, Welfare Economics, and Political Economy” to show how political economists should participate in this decision-making process—not as expert philosopher-kings, but as co-equals with their fellow citizens. Finally, we illustrate Buchanan’s system of thought in action by presenting two case studies: Virginia education policy in the wake of Brown v. Board of Education, and the 1928 Supreme Court ruling in Miller v. Schoene.