Upon the accession of the Nazis to power in Germany the Geheebs relocated to Switzerland, where they founded an alternative to their Odenwaldschule, the École d'humanité, and it was here that Ritsema met, towards the end of the course of his studies, his future wife, Catherine Gris, a young music teacher from Geneva.
After leaving the École d'humanité and subsequently obtaining his bachelor's degree Ritsema enrolled in the University of Geneva, but soon financial difficulties intervened as the outbreak of the Second World War put an end to the flow of money from the Netherlands.
Ritsema then worked at odd jobs to support himself, but continued voraciously to read on his own, particularly in French and German literatures, Tibetan Buddhism, and in Jungian psychology.
One year after his marriage to Catherine Gris, Ritsema removed with his wife to the Netherlands, where he obtained the position of Head of the Oriental department in the antiquarian division of E.J.
In 1956 Ritsema began to collaborate with Froebe and the Swiss zoologist and natural philosopher Adolf Portmann (1897–1982) in the planning of the Eranos Conferences.
This took twenty years to materialize, but was aided in its progress by various scholars, notably James Hillman and Robert Hinshaw (co‑founder of the Daimon Verlag of Einsiedeln, Switzerland).