The provocative paper by John Forrester ‘If p, Then What? Thinking in Cases’ opened up the question of case thinking as a separate mode of reasoning in the sciences. Case-based reasoning is certainly endemic across a number of sciences, but it has looked different according to where it has been found. This article investigates this mode of science – namely thinking in cases – by questioning the different interpretations of ‘If p?’ and exploring the different interpretative responses of what follows (...) in ‘Then What?’. The aim is to characterize how ‘reasoning in, within, with, and from cases’ forms a mode of scientific investigation for single cases, for runs of cases, and for comparative cases, drawing on materials from a range of different fields in which case-based reasoning appears. (shrink)