Bergson developed his radical ideas about the role of consciousness and the brain into a complete evolutionary theory, presented in Creative Evolution (1907), his most widely known work. He accepted Darwin's by-then triumphant idea that the organic forms of the present had evolved out of much earlier forms over long periods of time. But like many other thinkers, Bergson was unsympathetic to the strict determinist interpretation of evolution that had gained scientific support and popular credence. In its place he offered a vision of a creative impulse, the elan vital or life force, penetrating matter and driving evolution to higher forms of complexity and freedom. Bergson did, however, borrow one idea from Darwin's later interpreters. For Darwin, evolution proceeds through chance mutations that prove successful in the struggle to survive; such beneficial adaptations give an organism an advantage over its competitors. For Darwin's followers, the mind itself was just such an adaptation and evolved a s a useful tool for dealing with the demands of the environment. The intellect, then, was a strictly practical device, and its use was solely limited to dealing with the necessities of staying alive. One imminently useful way of doing this was to "carve" out of the seamless flow of experience, seemingly solid, discrete, and stable objects occupying an extended space. It would be most helpful in the struggle for suvival to recognize out of the "blooming, buzzing confusion" the tiger about to pounce on you, or the antelope you wish to eat. The difference between this kind of consciousness and a cosmic consciousness, open to the influx of the whole, is evident. The brain's function then, for Bergson, was to act as a "reducing valve," limiting the amount of "reality" entering conciousness. As he wrote in 1911, "The brain is the organ of attention to life," and the part it plays is that of "shutting out from consciousness all that is of no practical interest to us."
Cosmic consciousness, then, can be seen as a perception of the world not limited by or filtered through the brain. And a s most of us are compelled to "deal with" the world most of the time, it is clear why incidences of cosmic consciousness are rare. Yet one drawback to the brain's highly efficient ability to focus on necessities is that it "falsifies" reality, which, as Bergson earlier argued, is in truth a continuing flow of experience. The mind constantly takes snapshots, as it were, of reality, which enables it to orient itself admist the flux. The problem is that science, which takes the most comprehensive snapshots, makes the mistake of confusing photographs with reality itself.
We would, it seems, be left in a situation in which we are highly successful at dealing with the world, at the cost of losing contact with its reality. But, as Bergson argued in his essay "An Introduction to Metaphysics" (1903), the mind has another means of "knowing," aside from the rational intellect. This, he argued, was intuition. Just as we have an immediate, irreducible awareness of our own inner states, through intuition we have access to the "inside of the world. And that inside, Bergson argued, was the elan vital. Through drawing back from our habitual gesture of "dealing" with the world, we can, as Edward Carpenter experienced, discover a kind of consciousness in which subject and object--we and the world--are "one." This consciousness, Bergson argues is not necessarily associated with the brain. He argues that we perceive "virtually" much more than what actually reaches our conscious awareness. This would make sense, since that awareness is subject to the highly efficient editing procedures of the brain, which limits the amount of input coming to it through the senses. The whole past, for example, Bergson believed "still exists, ... is still present to consciousness in such a manner that, to have the revelation of it, consciousness has no need to go out of itself. ... It has but to remove an obstacle, to withdraw a veil." Such insights are the foundation of Marcel Proust's immense nove Remembrance of Things Past, perhaps the most determined effort to put Bergson's ideas into practice.
Lachman, Gary. A Secret History of Consciousness. Great Barrington, MA: Lindisfarne Books, 2003: 22-23.