Who is Socrates from Sacred Journey of the Peaceful Warrior and what is their importance?

Socrates is Dan Millman's former guru in Berkeley, CA, Socrates' name (and nickname Soc) comes up constantly in this book, which dovetails about midway through the Way of the Peaceful Warrior, where Socrates is a major character. A service station mechanic, Socrates teaches that it is better never to begin something, but once one begins, one must finish it. When he sends Dan off to assimilate his teachings, Socrates writes Mama Chia, his former lover, who he met in Tibet, to alert her to watch for Dan.