After retiring from biochemistry, he brought other long-time personal interests to the fore, becoming a writer in the fields of human potentials and the search for spiritual realisation.
Like many intelligent, humane people of his time, de Ropp was appalled by the staggering destruction and carnage that had occurred during World War I.
During a ten-year period working for the Lederle Laboratories near Pearl River, New York, de Ropp wrote a book for the general reader in the field of psychoactive substances (many of which are plant-derived): Drugs and the Mind.
[2] de Ropp's intense avocational interests, stemming largely from a spontaneous childhood spirituality, were nurtured by the influence of P. D. Ouspensky, whom he met in 1936.
"The work" (as the Ouspensky disciplines were termed) was an approach to establishing an integrated human awareness at a higher level — considered to be a true inner freedom.
[2] After arriving in the U.S., Robert de Ropp, by his own efforts, built two houses, one in Connecticut, another in New York state; he and his second wife, Betty, lived in Rockland County, NY.
[2] After working for the Lederle Laboratories for 10 years, de Ropp's attachment to the northeast U.S. waned, and he felt a pull to the West Coast.
In 1961 he purchased a small house on several acres, in Glen Ellen (slightly east of Santa Rosa, California), where the climate was mild and soil could be worked to high fertility.
[7] To support his family and finance their transition into the direct economy of living from the land and ocean, de Ropp worked until 1973 as a research scientist at the University of San Francisco.
In the book, Thompson writes that the name of the "acid guru" was "redacted at insistence of [his] publisher's lawyer," but in the original Rolling Stone article both Robert S. de Ropp and his residence on Sonoma Mountain Road are unredacted.
The first of these stands as his report on what he had learned from his teachers and from the writings of similar figures, as well as more mainstream psychologists, psychiatrists, and researchers into fields such as religion and the spiritual life.
The second is in part a sequential biography, and was written near the end of his life; a significant dimension of its content is his very personal evaluation of the characters and contributions of Gurdjieff, Ouspensky, Madame Ouspensky, John G. Bennett (another direct disciple of Gurdjieff), Gerald Heard, Aldous Huxley, Timothy Leary, Stephen Gaskin, Alan Watts, Carlos Castaneda, and other figures serving as teachers of those engaged in spiritual quests.
He is critical of those he views as false gurus or merely pompous, and attempts a fair-handed assessment of those he deems verbose but limited, whilst yet expressing genuine gratitude for those whose efforts he believes have enriched human life.