Denkpsychologie has been important for the development of psychology as well as of philosophy during the last century. More specifically, cognitive psychology as well as Karl Popper’s evolutionary epistemology were both influenced by Otto Selz’s cognitive psychology. Without doubt, Selz played a role in the development of Popper’s thinking, but Michel ter Hark has not given convincing evidence for Popper’s idea of bold conjectures being influenced by Selz.