Searching for the Searchlight Theory: From Karl Popper to Otto Selz

The aim of this article is to show that one of Popper's key ideas in epistemology, his so-called theory of the searchlight, is derived from early German Denkpsychologie, in particular the theory of schematic anticipations of Otto Selz. With his theory of schematic anticipations Selz intended to replace various forms of association psychology. Likewise Popper's theory of the searchlight aims to replace empiricism in epistemology (the Bucket theory, as he calls it). On the basis of Popper's still unpublished manuscripts on psychology between 1927 and 1931, it is shown that his position became increasingly Selzian. The term "Bucket theory" is used by him for the first time in an article in which he defends Selz, and in his earlier Ph.D. thesis there occur passages which show him in complete agreement with the theory of schematic anticipations. It is argued that Popper's Selzian stance in psychology finally enabled him to develop his characteristic deductive stance in epistemology and philosophy of science. It is also emphasized that Popper never credits Selz for this formative role.