Political epistemology is rich with thought experiments. Their most systematic function in the field is the construction of ideal theory. We present a sketch of a kind of political thought experiments, in fact, our preferred version of contractualist ones, in Scanlonian tradition. Following the contemporary pattern, we use some retouch: slightly idealizing the participants, making them reasonable and well informed. (Our brief example is an imagined debate about the moral status of migration and migrants). We offer an epistemically oriented analysis of the way contractualist political thought experiments function within the human cognitive apparatus, from mental modeling and simulation through empathy and sympathy to intuition. The whole process we describe, if successful, leads to understanding. And this providing of understanding, factual and normative, is a very important, if not indeed the most important role of thought-experimenting in political epistemology.