[1] Greer came to Druidry by way of the Order of Bards, Ovates and Druids in 1995 after some twenty years' involvement in Hermetic occult spirituality.
[2] He served as Grand Archdruid of the Ancient Order of Druids in America (AODA), an initiatory organization teaching Celtic nature spirituality, from 2003 to 2015.
[10] In a 2009 blog post entitled "Hagbard's Law", he contrasted the attention global warming receives compared to peak oil.
[13] Philosopher of science Jerome Ravetz summarized Greer's theory in his 2006 book chapter, titled "When Communication Fails: A Study of Failures of Global Systems.
Focusing on the election and opposition to Donald Trump as president of the United States, Greer predicts a continuing combination of magic and politics from the various class factions of the country.
Writing in The Futurist magazine, Rick Docksai declared that Greer's book The Ecotechnic Future is "as realistic a portrayal of the end of civilization as one is likely to find.
"[20] His book The New Encyclopedia of the Occult was selected as a reference text in 2005 by American Libraries[21] and noted by Booklist[22] and Publishers Weekly.