Descartes’ Philosophy: God’s Existence and Reality
Descartes’ Proofs for God’s Existence
Descartes’ tests for the existence of God are characterized by several key principles:
- Certainty from the Cogito: Part of the cogito, the existence of God is presented as the only other certainty.
- Beyond Deduction: No demonstration can be made purely by deduction, as this method was challenged by the second stage of methodic doubt. Instead, testing for God’s existence should extend the intuition of the cogito.
- A Posteriori and A Priori Tests: The first two proofs are a posteriori, based on an effect and applying the principle of causality. The third proof, concerning the content of the idea of a perfect being, is an a priori demonstration.
The Three Cartesian Proofs of God
Descartes presented three distinct proofs for God’s existence:
The Argument from the Idea of God (First Proof)
In our minds, God is conceived as an infinite and eternal substance. This idea is neither adventitious (derived from senses, as senses cannot conceive of anything eternal or infinite) nor factitious (created by us, as it imposes unchangeable characteristics of perfection). Therefore, the idea of God is an innate idea.
Descartes questioned the cause of this innate idea of infinity. He argued that although a thinking subject might be the cause of all their other ideas, they cannot be the cause of the idea of infinity because it exceeds their own degree of reality. If the cause must be proportionate to the effect, and the effect is the idea of infinity, its cause must be infinite. Thus, only God, as a truly Infinite Being, can be the cause of the idea of infinity present in the thinking subject.
The Argument from Our Own Existence (Second Proof)
Descartes, unlike Augustine of Hippo, denied that God is the direct cause of the subject’s existence in the same way. However, he asserted that one must admit that the subject himself cannot be the cause of his own existence. If the subject were his own cause, he would have endowed himself with all perfections contained in the idea of infinity. Since we find the subject to be finite, imperfect, and limited, he cannot have been his own cause. Therefore, we must conclude that God is the ultimate cause of our existence.
The Ontological Proof (Third Proof)
This proof, previously proposed by Anselm of Canterbury, was re-articulated by Descartes. He argued that the essence of a perfect Being necessarily contains existence. Therefore, one cannot conceive of a perfect Being that does not exist, just as it is unthinkable that a triangle lacks three angles. Since it is clear that it is possible to conceive of a perfect Being, it must necessarily exist.
Conclusions of the Cartesian System
Having established the existence of God, Descartes gained assurance regarding his criterion of truth. The actual existence of a perfect Being, combined with the conviction that this perfect Being is the creator of the thinking subject, allows Descartes to:
- Cancel the Evil Genius Hypothesis: Since the creator is infinitely good, the malevolent “evil genius” hypothesis is invalidated.
- Validate Clear and Distinct Ideas: It ensures that ideas perceived clearly and distinctly correspond with reality and are therefore true. This allowed Descartes to recover some realities previously eliminated by methodical doubt.
Clear and Distinct Perception of Reality
The Cartesian system only assures the existence of what is perceived clearly and distinctly. Regarding the external world, all that is clear and distinct is its extension (res extensa). For Descartes, this extensive substance, whose primary attribute is geometrical extension, means that only properties associated with this attribute can be perceived clearly and distinctly.
Key Aspects of Cartesian Doctrine: Mechanism
The Cartesian doctrine can be summarized by its embrace of a mechanistic model:
A Mechanistic Worldview
Mechanism is a theory prevalent among scientists and philosophers of modern times (with exceptions like Leibniz) regarding material reality. In this view, the world behaves like a machine. For mechanism, physical reality is a system of bodies in motion, with forces operating within a geometric or mathematicizable space.
Deterministic Nature
Mechanism is inherently deterministic. It posits that if all elements present in a state of matter are known, subsequent states can be predicted with complete accuracy. This mechanistic worldview largely disregards the theological vision of nature (which was fundamental in Aristotle’s philosophy). While Aristotle’s view included an unfolding under a prefigured plan, mechanism solely considers efficient causes, neglecting final and formal causality. Mechanical forces are seen as efficient causes, disconnected from other Aristotelian meanings of causality.
Reduction of Material Properties
Mechanism involves the reduction of properties of material reality. It excludes the so-called “secondary qualities”—those aspects of reality that cannot be translated into mathematical equations or quantifiable terms.