Philip E. Slater, a social critic and author, pursued success in the conventional way in the first half of his life. He studied hard, graduated from Harvard, became a tenured professor of sociology and wrote a best-selling book, “The Pursuit of Loneliness.”

The book, published in 1970, warned that a national cult of individualism and careerism threatened to turn America into a country of hypercompetitive loners ruled by tyrants. It sold some 500,000 copies, established Mr. Slater’s reputation and earned him hefty publishers’ advances.

It also marked the beginning of the second half of Mr. Slater’s life. Having re-examined his life through the lens of his own book, Mr. Slater decided in 1971 to resign as the chairman of the sociology department at Brandeis University, where he had taught for 10 years, and take a different path. He took up acting, wrote novels and began culling his personal possessions down to the two boxes he left when he died at 86 on June 20 at his home in Santa Cruz, Calif. The cause was non-Hodgkin’s lymphoma, said his daughter, Dashka Slater.

He founded Greenhouse, a personal growth center, in Cambridge, Mass., with Jacqueline Doyle, a writer, and Morrie Schwartz, a fellow sociology professor at Brandeis (later known as the subject of the Mitch Albom best seller “Tuesdays With Morrie”).