I listed here many of the teachers and thinkers whose influence I have felt.   In his wonderful new book on John Cage’s 4′ 33”, the indefatigable Kyle Gann says this (pages 71-72):

The meme that Cage was more of a music philosopher than a composer has become commonplace, most of all, it seems, among people who don’t like his music and are in need of a way to justify his celebrity.  Cage was not a philosopher in any sense that the philosophy profession would recognize, but he was very much a composer who drew inspiration for his music from philosophical ideas.  The list of artists, writers, and thinkers he names in justification of his musical trajectory is a long one:  Meister Eckhart, Huang-Po, Kwang-Tse, Erik Satie, Henry David Thoreau, Gertrude Stein, Arnold Schoenberg, John Cage Sr., Marcel Duchamp, Sri Ramakrishna, Daisetz Sukuki, Joseph Campbell, Ananda K. Coomaraswamy, Alan Watts, Antonin Artaud, Robert Rauschenberg, Morton Feldman, David Tudor, Norman O. Brown, Marshall McLuhan, Buckminster Fuller, Gita Sarabhai, and Christian Wolff, among others.”

I was reminded of James Pritchett’s intention, when writing his book on Cage’s music, to as much as possible read everything that John Cage had himself read, and in the order he had done so.
References:
Kyle Gann [2010]: No Such Thing as Silence.  John Cage’s 4′ 33”.  New Haven, CT, USA:  Yale University Press.
James Pritchett [1993]:  The Music of John Cage.  Cambridge, UK:  Cambridge University Press.