* Simple consciousness, possessed by both animals and mankind.
* Self-consciousness, possessed by humankind, encompassing thought, reason, and imagination.
* Cosmic consciousness, which is "a higher form of consciousness than that possessed by the ordinary man."

According to Bucke, "This consciousness shows the cosmos to consist not of dead matter governed by unconscious, rigid, and unintending law; it shows it on the contrary as entirely immaterial, entirely spiritual, and entirely alive; it shows that death is an absurdity, that everyone and everything has eternal life; it shows that the universe is God and that God is the universe, and that no evil ever did or ever will enter into it; a great deal of this is, of course, from the point of view of self-consciousness, absurd; it is nevertheless undoubtedly true."

First published in 1901, this classic work is the magnum opus of Bucke's career, a project that he researched and wrote over many years. In it, Bucke described his own experience with cosmic consciousness, that of contemporaries (most notably Walt Whitman), and the experiences and outlook of historical figures including Buddha, Jesus, Paul, Plotinus, Muhammad, Dante, Francis Bacon, and William Blake.

The author observes, "The person who passes through this experience will learn in the few minutes, or even moments, of its continuance more than in months or years of study, and he will learn much that no study ever taught or can teach." After reading Bucke's writings, philosopher P. D. Ouspensky wrote, "Cosmic Consciousness is, as its name implies, a consciousness of the cosmos, that is, of the life and order of the universe. Along with the consciousness of the cosmos there occurs an intellectual enlightenment or illumination which alone would place the individual on a new plane of existence--would make him almost a member of a new species."

This large-format facsimile of the 1905 edition is notable for its superb design and typography, making it a pleasure to read.