Ian Hacking (1936–2023) was an influential philosopher of science whose writings continue to bring insight into issues in theoretical and philosophical psychology. Hacking applied his interdisciplinary perspective to many topics, such as the cultural and political aspects of psychiatric classifications, the nature of human and natural kinds, the epistemological implications of social constructionism, and the historical contingencies that shape the construction of scientific concepts. This chapter provides an outline of some of Hacking’s most relevant work for theoretical and philosophical psychology by focusing on historical ontology, looping effects, and making up people.