Monism is the view that the universe, at the deepest level of analysis, is one thing or composed of one fundamental kind of stuff. This is usually contrasted with Substance Dualism, the view found for example in the writings of Plato and Descartes that, fundamentally, the universe is composed of two kinds of stuff, physical stuff and the stuff of soul, mind or consciousness. Reflexive Monism, a philosophical position developed by Max Velmans to account for the problems of consciousness in his book Understanding Consciousness, is a modern version of an ancient view that the basic stuff of which the universe is composed has the potential to manifest both physically and as conscious experience (a dual-aspect theory in the tradition of Spinoza).
In its evolution from some primal undifferentiated state, the universe differentiates into distinguishable physical entities, at least some of which have the potential for conscious experience, such as human beings. While remaining embedded within and dependent on the surrounding universe and composed of the same fundamental stuff, each human, equipped with perceptual and cognitive systems has an individual perspective on, or view of, both the rest of the universe and him or her self. In this sense, each human participates in a process whereby the universe differentiates into parts and becomes conscious in manifold ways of itself, making the entire process reflexive. Similar views are found, for example, in later Vedic writings such as the Upanishads.