Descartes’ Philosophy: Soul, Body, and the Existence of God
To Descartes, a substance is something that can exist by itself without any other substance. The thinking substance (res cogitans) is the immortal soul. The absolute independence of thought proves the existence and immortality of the soul.
Among the mental contents, ideas are images of things and the real objective of our knowledge. There are three types of ideas:
- Adventitious ideas: These seem to come from an outside world through sensory assumptions (e.g., the sense of my body, as perceived by the senses, like a table).
- Factitious ideas: These are thoughts constructed from other ideas by deduction (e.g., a unicorn, which is the union of two things).
- Innate ideas: These are simple ideas that are not derived from external sources. They belong to the same thinking process and are innate rather than Platonic. They are innate to reason, and among them stands out the idea of God, or infinity, or perfection.
The idea of God is innate, not derived from experience, imagination, or fantasy. From the clearness and distinctness of the idea of God, Descartes believes he can demonstrate the actual existence of God as a substance other than his own self and the mental world. According to Descartes, God is an innate idea because if I am finite and imperfect, the origin of an idea that represents infinite and absolute perfection cannot come from myself. Therefore, there must be a being that possesses these perfections, through which I may have this notion of perfection. We must recognize that God exists as the origin of the idea of Him that I have in my mind.
The idea of God is like the seal of the architect (the brand that makes the man), showing the existence of God as the infinite creator and preserver of my being.
At this point, it is necessary to prove the existence of corporeal realities, i.e., material things that supposedly exist outside of my mind.
We doubted the outside world thanks to the possibility of the existence of an evil genius, denying its existence or the information I hear in this world. But the very demonstration of the existence of God eliminates deductively the hypothesis of the evil genius, because this God of infinite perfection, power, and goodness cannot act in bad faith, and having created us such that even in the clear and distinct ideas we are wrong.
Once we acknowledge that there is a world of bodies, we ask what a body is. Bodies, by their property of being extended by the attribute of extension, can change shape and location. Bodies have primary qualities (length, width, and depth) and secondary qualities (color, smell, temperature, sound). The primary qualities can be known in mathematical terms and are clear and distinct ideas that are matched in the real world.
In the same way that the soul is the res cogitans (soul), the body is the res extensa (matter).
Soul-Body Dualism
Thought itself is the foundation. This evidence showed us the cogito that makes the self or soul a substance whose whole essence and nature is nothing more than thinking, and that there is no need for any place, nor does it depend on any material thing. The cogito is the demonstration that the spiritual soul is essentially free and independent. But between soul and body (res extensa) a union is allowed, but it is injured by bodily phenomena that have an impact on the soul, and the decisions of the spirit running through the body. There is therefore a difficult to explain dependence of the two substances which by definition are essentially independent. Descartes uses a newly discovered brain area at the time, the pineal gland. What is clear is that both the soul (res cogitans) and body (res extensa) are independent substances that are independent of each other to exist. What they both depend on for their existence is an infinite substance called God. They are therefore two finite substances that rely on a finite substance.
Meditations on First Philosophy
Meditations on First Philosophy is Descartes’ major work. It recounts the author’s intellectual journey in search of truth. It consists of six parts and demonstrates a raw and analytical mind constantly seeking clarity in expression.