Mind at Large is a concept from The Doors of Perception and Heaven and Hell by Aldous Huxley. This philosophy was influenced by the ideas of C. D. Broad. Psychedelic drugs are thought to disable filters which inhibit or quell signals related to mundane functions from reaching the conscious mind. In the aforementioned tomes, Huxley explores the idea that the human mind filters reality, partly because handling the details of all of the impressions and images coming in would be unbearable, partly because it has been taught to do so. He believes that psychotropic drugs can partly remove this filter, which leaves the drug user exposed to Mind at Large. Huxley was administered mescaline, and had an interviewer prompt him to comment on various stimuli around him, such as books and flowers. The conversation was recorded and the book mainly concerns Huxley's thoughts on what he says in the recordings. He observed that everyday objects lose their functionality and suddenly exist "as such." Space and dimension become irrelevant, and perceptions seem to be enlarged and at times even overwhelming.
Each person is at each moment capable of remembering all that has ever happened to him and of perceiving everything that is happening everywhere in the universe. The function of the brain and nervous system is to protect us from being overwhelmed and confused by this mass of largely useless and irrelevant knowledge, by shutting out most of what we should otherwise perceive or remember at any moment, and leaving only that very small and special selection which is likely to be practically useful. According to such a theory, each one of us is potentially Mind at Large.
In The Doors of Perception, Huxley also stated: "In the final stage of egolessness there is an 'obscure knowledge' that All is in all—that All is actually each. This is as near, I take it, as a finite mind can ever come to 'perceiving everything that is happening everywhere in the universe.'"