Descartes' Philosophy: Cogito, Substance, and Dualism

The First Truth: Cogito

From that universal doubt appears the first truth and certainty. The first base of Cartesian philosophy is: "I think, therefore I am." The cogito is not an argument, but an intuition.

Try to explain rationally the universe, i.e., to explain in terms of man, according to me. It was therefore necessary to start by defining the man, the self, and defining it so that in him were enough elements to build a world system.

The cogito is an act of the subject because I'm the one who thinks.

The ideas represent an inevitable mediation between the thinker and things.

Three Types of Ideas

• Innate: The understanding that has by nature: thought, God.
• Adventitious: Those who come from outside expertise.
• Artificial: Those coming from our imagination.

True knowledge is by means of innate ideas, that reason is in itself, and the content in these ideas is presented in a clear and distinct line with reality.

Reason and Reality: The Theory of the Three Substances

Defines the substance as "a thing that exists in such a way that it does not need anybody else to exist." The Cartesian system leads to three clear ideas that correspond to the three substances called: thought, self, and material things or bodies.

The Thinking Substance

The thinking self is the first substance that is the first truth or certainty. The fundamental attribute of this substance is thought or consciousness.

The Infinite Substance

The second substance is God. For Descartes, the thinking self is not perfect but has the idea of perfection. This idea, born with us (innate), is the idea of a perfect being who is God. God is a substance infinite, eternal. God is a guarantee of veracity.

Descartes presents three proofs for the existence of God:

• The idea of perfect and infinite: The finitude that I recognize in myself is the opposite of infinity that I know God. He is the necessary cause of the idea of him in me. "The existence of God is demonstrated by its effects, just for the fact that the idea we have about him is in us."
• The contingency of the self: Just as I am not infinite and I have all the perfections, the being who has all the perfections is caused by this fact itself and therefore necessarily exists.
• The ontological argument: The outline of the proof is the following: existence is a perfection, God has all perfections, then has existence.

The Extended Substance

Material things. This substance is a fundamental attribute of the extension.

Descartes's physics is mechanistic. Everything in the world is a geometric mechanism.

The cause of the movement is twofold. A cause which, in general, has created and introduced in the field, and this cause is God. After entering the motion on the matter, God does not intervene again, if not to continue to keep the matter in his being.

Three Laws of Motion:

• Law of inertia: Every thing is always in the same state until it is changed by any external cause.
• Law of direction of motion: A body in motion tends to continue straight along the tangent to the curve describing the phone.
• Law of shock: The clash between two moving bodies is not lost, but their number remains constant.

The Theory of Matter

Matter is nothing but space, pure extension, the object of geometry. Matter comes down to the extension.

We can say that not only the physical universe but also plants, animals, and the human body are pure mechanisms. There are only mechanical forces acting on the universe. All beings are like machines built by God.

Anthropological Dualism

Descartes, like Plato, separates the soul and body, thereby establishing dualism. The soul belongs only to thinking. The body is reduced to a machine governed by the laws of physics, and life to a mechanical movement.

The soul is united to the body, realizing that unity in the pineal gland, which is at the center of the brain. It melted bodily sensations, and through it, the soul receives organic stimuli. Considers that it is the soul that feels, not the body. It is the soul that receives and suffers the passions.