Final answer:
René Descartes believed the mind and body were separate entities, a view known as Cartesian dualism. He used 'Cogito, ergo sum' to argue for the mind's distinct existence. However, contemporary findings in neuroscience challenge this dualistic perspective.
Step-by-step explanation:
The philosopher who believed that the mind and body were distinct and separate entities was René Descartes. He posited a form of substance dualism where the mind, characterized as a non-physical 'thinking thing' (res cogitans), was fundamentally different from the body, described as an extended nonthinking thing (res extensa). This distinction lies at the heart of Cartesian dualism, which asserts that reality is composed of two fundamentally different substances: the physical (matter) and the non-physical (spirit).
Descartes famously declared, 'Cogito, ergo sum' ('I think, therefore I am'), indicating his belief that the ability to think is proof of the existence of the mind as a separate entity from the body. Despite his arguments, modern science challenges Descartes' view with evidence suggesting that cognitive processes cannot occur without a physical brain.