Wayne Dyer, the author and speaker whose best-selling book Your Erroneous Zones (1976) offered millions a framework to potentially improve their lives, has died at age 75.

Dyer died in Maui, Hawaii, on Saturday, according to NBC News.

The cause of death has not yet been revealed, although Dyer was diagnosed with chronic lymphocytic leukemia in 2009 — which he claimed to have treated with “psychic surgery” by Brazilian spiritualist João Teixeira de Faria, as well as through regular exercise and positive thinking, NBC says.

His best-known work, Your Erroneous Zones, was based on the philosophies of Siddha Yoga founder Krishna Rau, who was better known as Swami Muktananda. The book surged to the top of the best-seller list and catapulted Dyer to instant fame. He would go on to appear on every major talk show in the U.S. and became a fixture on television network PBS for over 40 years.

His death prompted an outpouring of condolences from those he had made an impact upon, including celebrities like Ellen DeGeneres (whose wedding he officiated) and Oprah Winfrey.

Dyer had eight children and was separated from his third wife when he died.

[NBC News]

Read next: 30 Self-Help Books That Permanently Changed My Life

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Write to Rishi Iyengar at rishi.iyengar@timeasia.com.