This chapter provides a historical overview of influential cases of ideologically motivated pseudoscience, including phrenology, eugenics, Nazi physics, Lysenkoism, IQ testing, and the theory of everything. It then examines in more detail sociobiology and evolutionary psychology as examples of disciplines involving a basis in genuine scientific research, but which often lapse into ideology, arguing for the need to draw lines of demarcation between what is scientific and what is ideological within these disciplines. The discussion is framed in terms of the distinction between the openness of scientific discovery and the closure of ideology.