In the 18th century, David Hume suggested that the “science of man” (psychology) was the foundation for all other sciences (philosophy). Now a latter-day Hume offers a model of mentality that sets psychology and philosophy on common footings, eliminating the breach between the sciences and the humanities. From this backdrop, the author offers solutions to some of the great questions: the nature of reality, value, certainty, validity, free will, morality, and justice.