Scholars such as Robert Thurman and Huston Smith appraised it as the best book written on the subject.

In 2001, Huston Smith disputed Kripal's work as "colonialism updated".

(original publication, 1973; foreword by Huston Smith, 1996 edition)

A foreword by Huston Smith was first included in a 1979 edition.

Huston Smith describes early Buddhism as psychological rather than metaphysical.

The American religious scholar Huston Smith who studied with Zuigan for fifteen years.

Contrary to Zaehner, Huston Smith draws attention to evidence suggesting that these drugs can facilitate theistic mystical experience.

Similarly, forty years later, Huston Smith, a religious scholar, wrote that in The Perennial Philosophy:

Huston Smith wrote a foreword to the 3rd edition.

Heard is also responsible for introducing the then unknown Huston Smith to Huxley.