A true thinking type, Dr Weiss was well established in his career as an MD when he met a patient, "Catherine", who would change his life. It is through this journey and evolution that DR Weiss developed character traits of an Intuitive Feeling type. You can hear the love, peace and idealism of NFs as described by David Keirsey in not only how DR Weiss speaks but every word he says. But this path - from his mind to his heart - was not an easy one for Dr Weiss. Meeting Catherine, who experienced a spontaneous past life regression while under hypnosis, was deeply challenging to his understanding and scientific mind. His journey from being an agnostic to the man in the videos above is described beautifully and in detail in Many Lives, Many Masters.
BTW, the Masters is the name Dr Weiss gives to the place/space we go to to rejuvenate and refresh before embarking on another life. You can learn more about Dr Weiss's experiences both with this state between lives and with past life regressions with other patients in Messages from the Masters.
As a result of the scientific method, and Dr Weiss's research into peer reviewed journal articles and conversations with peer professionals, past life regressions are now widely used as an accepted spiritual healing modality.
This is the foundation of Dr Weiss's book: Many Lives, Many Masters.