Descartes' Cogito and Metaphysical Proofs

The Cartesian Doubt and the Self

The Cartesian doubt leads to the existence of an unquestionable I think, a substance that thinks, the res cogitans or soul.

Types of Thinking

There are several kinds of thinking:

• Volition (wishes), which may or may not be true.
• Trials, which are uncertain regarding their truth.
• Ideas, which are the only truly certain thoughts, representing mental concepts.

Classification of Ideas

Ideas can be classified based on their origin:

• Adventitious or Acquired: Ideas that originate from the external world.
• Factitial or Artificial: Ideas that we invent ourselves.
• Innate or Natural: Ideas that do not proceed from the external world nor are constructed by us, but arise from our own thinking.

Demonstrating the Existence of God

Descartes offers several arguments for God's existence:

Causality Argument

I know that I am imperfect and capable of doubt or error. I possess the idea of perfection. This idea must be innate, as only a perfect being—God—can cause the idea of perfection in an imperfect being. An imperfect being cannot cause the idea of a perfect being.

Contingency of the Self

If I were my own creator, I would possess all the qualities I conceive of, but I am imperfect and have not created myself. Therefore, there must be an external creator.

Ontological Argument

A perfect being must possess all perfections: infinity, eternity, truthfulness, goodness, etc. If we consider the idea of True Perfection, this perfect being must exist, because existence is a perfection.

By demonstrating the existence of God, Descartes breaks with the possibility of a malignant genius. Since God is the guarantee of knowledge and certainty, Descartes proves God's existence not through faith, but through reason.

Outside World (Cartesian Anthropology)

We observe differences between the idea of the thinking self and the idea of the extended body (anthropological dualism). I can doubt the body, but not my thinking. However, the goodness of God guarantees that our senses, when subordinated to reason, do not deceive us regarding the existence of extended things. We gain certainty of a finite, created substance, the corps (body), whose attribute is extension. This constitutes the third substance in Cartesian metaphysics.

This substance has qualities:

• Primary: Those the mind perceives clearly and distinctly (e.g., position, motion, magnitude).
• Secondary: Those not immediately present or clearly distinct, perceived subjectively.

Union of Mind and Body

Descartes describes the union between the thinking substance (res cogitans) and the extended substance (res extensa) as the union of issue. This union occurs in the pineal gland, located in the center of the brain, where the soul connects to the body.

Mechanicism and Freedom

The body is governed by mechanical laws. If the self were not a substance separate from and completely detached from the body, there would be no room for freedom. Descartes' ability to doubt everything stems from his freedom as a thinking substance.

The mechanism arising from anthropological dualism had both positive and negative implications:

• Advancement of Medicine: Machines are dismantled, and the body is viewed similarly, favoring medical progress.
• Implications for Nature: If all matter and machines constitute nature, humans might feel entitled to treat matter and animals as they wish.