After his mother died, his father married the economist Ruth P. Mack, through which he had a half-sister, Mary Lee Ingbar, a pioneer of computer analysis who became a professor at Dartmouth College and University of Massachusetts Medical School.

In 1961, he returned from military service in Japan, continuing at the Massachusetts Mental Health Center and Boston Psychoanalytic Society and Institute, receiving certification in child and adult psychoanalysis and psychotherapy.

He addressed this issue of "world view" on the individual level in his early clinical explorations of dreams, nightmares and teen suicide, and in A Prince of Our Disorder, his biographical study of the life of British officer T. E. Lawrence, for which he received the Pulitzer Prize for Biography in 1977.

[10] In the 1980s, Mack interviewed many international political figures as part of his research into the root causes of the Cold War, including former United States President Jimmy Carter and the "father of the hydrogen bomb", Edward Teller.

[11] In the early 1990s, Mack commenced a decade-plus psychological study of 200 men and women who reported recurrent alien encounter experiences.

[12] Many of those he interviewed reported that their encounters had affected the way they regarded the world, including producing a heightened sense of spirituality and environmental concern.

Literature professor Terry Matheson writes that "On balance, Mack does present as fair-minded an account as has been encountered to date, at least as these abduction narratives go.

[citation needed] His later research broadened into the general consideration of the merits of an expanded notion of reality, one which allows for experiences that may not fit the Western materialist paradigm, yet deeply affect people's lives.

According to Daniel P. Sheehan, one of Mack's attorneys, the committee's draft report suggested that "To communicate, in any way whatsoever, to a person who has reported a ‘close encounter’ with an extraterrestrial life form that this experience might well have been real ... is professionally irresponsible.”[22] Upon the public revelation of the existence of the committee (inadvertently revealed during the solicitation of witnesses for Mack's defense, ten months into the process), questions arose from the academic community (including Harvard Professor of Law Alan Dershowitz) regarding the validity of an investigation of a tenured professor who was not suspected of ethics violations or professional misconduct.

[25] On Monday, September 27, 2004, while in London to lecture at a T. E. Lawrence Society-sponsored conference, Mack was killed by a drunk driver heading west on Totteridge Lane.

The driver, Raymond Czechowski, an IT manager, was arrested at the scene and later entered a plea of guilty to careless driving while under the influence of alcohol.

"Although this was a tragic event for our family," the letter reads, "we feel [the accused's] behavior was neither malicious nor intentional, and we have no ill will toward him since we learned of the circumstances of the collision."

[27] He wrote the following books: Collaborations: He was editor or co-editor of: Unpublished: He also wrote the foreword to Paths Beyond Ego: The Transpersonal Vision (1993), the introductions to The PK Man: A True Story of Mind Over Matter (2000) by Jeffrey Mishlove and Secret Life (1992) by David M. Jacobs, and he contributed chapters to several books including The Long Darkness: Psychological and Moral Perspectives on Nuclear Winter (1986), The Psychology of Terrorism Vol.