Radical Doubt and the Cogito in Descartes' Meditations

Universal Doubt

The senses can deceive us (Dream Argument).

Extreme Skepticism

Even math could be false if an evil demon deceives us.

Universal Doubt

The senses can deceive us (Dream Argument).

Extreme Skepticism

Even math could be false if an evil demon deceives us.

Only Certainty

Everything can be doubted except one's own thinking.

Cogito Argument

Doubting proves thinking, and thinking proves existence.

Indubitable Truth

"I think, therefore I am" is self-evident and certain.

Wax Argument

Physical objects change, but the intellect understands their essence.

Mind vs. Body

Knowledge of the thinking mind is clearer than of the body.

Causal Argument

Every idea must have a cause.

Idea of God

The concept of an infinite being cannot come from a finite mind.

Necessary Cause

Only an infinite being (God) could be the source of this idea.

Ontological Argument

Just as a triangle must have three sides, God's essence includes existence.

Necessity of God

Since God is perfect, He must exist.

God and Truth

God is no deceiver, so clear and distinct perceptions are reliable.

Mind-Body Distinction

The mind is a thinking, non-extended substance; the body is extended and non-thinking.

Dualism Argument

Since the mind can exist without the body, they must be distinct.

Proof of the External World

Sensory perceptions occur involuntarily, implying an external cause.

God's Role

Since God is not a deceiver, external reality must exist.

Mind-Body Interaction

The body influences the mind (pain, hunger), and the mind controls the body (movement).

Pineal Gland Theory

Descartes speculated that the pineal gland mediates the mind-body connection.