Growing up in the suburbs of Boston and raised on secular Judaism, Cocoa Puffs, and Gilligan's Island, Peter Bebergal was barely in his teens when the ancient desire to finding higher spiritual meaning in the universe struck. Already schooled in mysticism by way of comic books, Dungeons & Dragons, and Carlos Castaneda, he turned to hallucinogens, convinced they would provide a path to illumination.

Was this profound desire for God--a god he believed that could only be apprehended by an extreme state of altered consciousness--simply a side effect of the drugs? Or was it a deeper...