The mind is the faculty of thought, perception, emotion, and reasoning. It is what thinks, feels, and decides. It is not the brain, though it depends on the brain. The mind is what the brain does, or so many philosophers argue. Others hold that the mind is a separate substance, or that it is identical to the brain, or that it is a pattern of information processing. The debate is one of the oldest in philosophy and one of the most active in cognitive science.

Descartes argued that the mind is a thinking substance, distinct from the body. Locke treated it as the seat of personal identity, grounded in memory. Hume argued that there is no unified self, only a bundle of perceptions. Kant argued that the mind actively organizes experience through categories. In the 20th century, philosophers and scientists debated whether mental states are physical, functional, or irreducible. The mind is studied by psychology, neuroscience, artificial intelligence, and philosophy. Each discipline brings its own methods and assumptions. The result is a rich but fragmented picture, with no single account commanding consensus.

Faculties of mind

• Perception. Sensing and interpreting the world.
• Reasoning. Drawing inferences and making judgments.
• Emotion. Feeling and evaluating.
• Memory. Storing and retrieving information.
• Will. Choosing and acting.

The mind is not a thing but a set of capacities. That is part of why it is so hard to define.