During his study years he founded the Dutch section of the English Practical Idealists Association (PIA), a youth movement aimed at initiating a paradigm shift of the spiritual mind amongst students.
Just like his brother Cees, he was closely involved with hosting the annual Order of the Star camps at the Eerde estate in Ommen.
This property was owned by Philip baron van Pallandt and it was here that Krishnamurti had settled his Order of the Star in the East.
J.J. van der Leeuw became a priest in the Liberal Catholic Church and treasurer of the Manor, the villa owned by the Theosophical Society in Sydney.
Back in the Netherlands van der Leeuw was elected as president of the Dutch Section of the Theosophical Society from 1930 until 1931.
In the early Thirties Van der Leeuw traveled the world to elaborate on his social-scientific and philosophical ideas.
Van der Leeuw lived in London, but during 1933 was a regular visitor of Sigmund Freud in Vienna, where he was being analyzed.