This is the last of Mechner’s four articles on the topic of aesthetics. It builds on the other three and elaborates on the following issues: the conditions in which aesthetic reactions occur, their construction, their behavioral and biological origins, and the useful functions they perform in societies and cultures. It extends the analysis of aesthetics into the interpersonal and socio-cultural domains. It explores the role aesthetic sensibilities may have played in the evolution of language, inquiry skills, and manipulation of the concept repertoire. It also examines the tendency to look for and find the causes of events in the external environment rather than in one’s own learned perceptions based on one’s idiosyncratic history, resulting in a vast array of human illusions and biases.