Final answer:
Descartes established the Existence of God in the fifth meditation and is known for his dualistic philosophy, which posits the mind as a separate, non-physical entity from the body.
Step-by-step explanation:
In the fifth meditation, René Descartes established the concept of the Existence of God, rather than dualism, the scientific method, or materialism. However, it's worth noting that dualism is a central theme throughout his meditations. Descartes' meditations culminate in his famous statement, Cogito, ergo sum: I think, therefore I am, which is the foundation for his argument on the separateness of the mind and body, asserting the existence of the mind as a distinct, non-physical entity - an essential part of dualism.
René Descartes posited that reality consists of two fundamentally different substances: the material and the non-physical, or the realm of the mind and consciousness, separate from the physical body. This philosophical position is known as substance dualism, where the mind (res cogitans) is understood as a 'thinking thing' that exists independently of the physical body (res extensa). Modern critiques, however, lean on the evidence provided by neuroscience which indicates that thought is inextricably linked to the physical brain.