The notion that reality is ultimately grounded in consciousness rather than in a physical substratum occurs often as a mentation in altered states of consciousness, psychedelic or otherwise. This, however, is diametrically opposed to the conventional doctrine of the physical sciences, which maintains that the physical universe is the only, or at least the fundamental, form of reality. Does this mean that physical science requires us to dismiss the notion that everything is ultimately consciousness? Is this mentation a delusory artefact of altered states? No. This paper argues for a cogent and rational philosophy that defends mental monism - the principle that fundamental reality is of the nature of a conscious mind - without violating anything in science itself. This is a philosophy advocated by Adi Shankara in the Advaita Vedanta school of Hinduism, and by Bishop George Berkeley’s Subjective Idealism. Filmed at Breaking Convention 2017 4th International Conference on Psychedelic Consciousness University of Greenwich London - June 30th - July 2nd 2017 https://www.breakingconvention.co.uk