Having passed examen artium in 1955, Setreng underwent technical training at Kjevik with the Royal Norwegian Air Force, and subsequently worked with maintenance of aircraft at Gardermoen Air Station. Through reading of Laozi and Kafka, he developed an interest in philosophy, and from 1958 he started studying at the University of Oslo. Interested in nature and environmental protection, and influenced by Arne Næss, Peter Wessel Zapffe and Henri Bergson, he eventually developed his own original variant of ecophilosophy. He graduated as cand.mag. in 1966, with the thesis, Musikk-kritikk og kommunikasjon. In 1970 he took actively part in protests against development of the waterfall of Mardalsfossen. An able mountain climber, he travelled to Rolwaling Himal to study the Sherpa people native to Nepal and the Himalayas, and fascinated by their way of thinking, he converted to Buddhism. In the late 1970s he was engaged in the Alta controversy and in protests against construction of the Innerdalsvatnet dam in the Orkla River.