The early research of Karl Popper both in psychology and in philosophy of science is described; its basis for his later breakthroughs in the philosophy of science is explained. His debt to Otto Selz’s thought psychology is thereby detailed. Otto Selz’s philosophy of science is then explained, and its conflict with Popper’s early as well as his later views is portrayed. These studies of the conflicting views of Popper’s early views and Selz’s philosophy of science provide the basis for demonstrating the mistakes that Michel ter Hark has made in claiming that the alleged originality of Popper’s views occurred only in the 1970s and are little more than a rehash of Selz’s alleged evolutionary epistemology.