 “Conceptual constructivism”, as we could call it, is among the empiricist alternatives to the argument view. The position has been taken up by Van Dyck (2003) to account especially for Heisenberg’s ɣ-ray microscope; but also by Gendler (1998) to makes sense of Galileo’s falling body thought experiment. Gendler’s proposal was advanced in more general terms by Camilleri (2014) in order to establish a firm middle ground between the views of Norton and Brown. Conceptual constructivism was first proposed by Thomas Kuhn (1964). He employs many of the concepts (but not the terminology) of his well-known Structure of Scientific Revolutions. On his view a well-conceived thought experiment can bring on a crisis or at least create an anomaly in the reigning theory and so contribute to paradigm change. Thought experiments can teach us something new about the world, even though we have no new empirical data, by helping us to re-conceptualize the world in a new way. Accordingly, Fehige (2013b) entertains the option of conceptual constructivism in form of a Neo-Kantian reading of Einstein’s famous clock in the box thought experiment. This proposal is inspired by Michael Friedman’s proposal to conceive of scientific revolutions as times when a Kantian kind of natural philosophy plays a major role in guiding scientists from one paradigm to another. The work of Kuhn left us with a puzzle: if scientific rationality is absolutely dependent on a paradigm, and if during scientific revolutions one paradigm replaces another, not in degrees but like a Gestalt switch, then this transition from one paradigm to the next cannot be a matter of scientific rationality. Are scientific revolutions irrational periods in the history of science? Not necessarily, some kind of natural philosophy may guide the process. Friedman has a Kantian natural philosophy in mind; his proposal did not earn wide acceptance, but the problem remains (see Fisch 2017).