Descartes’ Philosophy: Doubt, God, and the Criterion of Truth
Descartes’ Philosophy
Notions
1. Doubt and Certainty
Descartes raises the question of Epistemology, the study of knowledge. He proposes that all information should be revised to dispel any suspicion of error, and that the truth is guided by a theoretical method. Methodical Doubt is the use of doubt as a way forward, as a procedure for finding the truth. It involves doubting everything in which the slightest doubt can be found.
This questioning is required by the first rule of his method, which requires considering as true only the obvious, i.e., what is presented to our mind clearly and distinctly.
Descartes reviews all possible information channels:
- Senses (doubtful)
- Reasoning or deduction (doubtful)
- Distinction of reality (sleep vs. wake, doubtful)
The last moment of doubt is the evil genius hypothesis, a powerful evil being that makes us fall into errors even in the ideas we perceive as obvious. Cartesian doubt is characterized by being universal, methodical, skeptical, provisional, and theoretical.
The primary certainty for Descartes lies in the proposition “I think, therefore I am” (cogito ergo sum). This is not obtained by reasoning, but captured by intuition. To ensure the criterion of truth and distinction outside of the mind, Descartes turns to the existence of God as a benevolent creator, willing to get rid of the evil genius.
2. Thoughts and Ideas
Thought is the essential attribute of the thinking substance, which assures us of our existence. Thinking encompasses understanding, willing, imagining, feeling, etc. Descartes discards the scholastic view that thought rests on things, instead proposing that thought rests on ideas.
For Descartes, the idea is the content of thought, and thought rests on ideas, not on things whose existence is questionable. Ideas are mental contents that depend on the subject who thinks at that moment; they are the materials with which the mind works. These ideas have been placed in the subject by God. Innate ideas coincide with the true (clear and distinct) since the existence of a benevolent divinity ensures their correspondence with reality.
There are 3 types of ideas:
- Adventitious ideas: from external experience, realities external to the self (e.g., the idea of the sun).
- Factitious ideas: incorporated from other ideas (e.g., wealth, unicorn).
- Innate ideas: from our own nature (e.g., the idea of thinking, existence).
Descartes distinguishes between: objective reality (belonging to ideas), their own formal reality, and the eminent reality of objects (less accurate than formal reality).
Cogito and Assurance Criteria
Descartes begins by deliberately doubting all possible knowledge. Methodical doubt, a philosophical inquiry procedure, uses doubt as a way forward, extending to our senses, reasoning ability, and making us unable to distinguish reality from dream. We also find the hyperbolic doubt represented by the Evil Genius.
By doubting everything, we find an undeniable truth:
“I think, therefore I am” (Cogito ergo sum).
This truth is not the conclusion of an argument, but a productive process in which we are aware that even if we are deceived and everything is false, it is clear that we are the ones who doubt. This truth can refute the theories of skeptics.
Another problem arises: the narrowing of doubt reduces everything to the statement of the thinking self. To resolve this, Descartes explains other truths contained in the first one: the essence of self, the criterion of truth, and the need for God in his system.
The essence of self is thinking; “I am a thing that thinks,” a thinking substance. This statement is the second Cartesian truth. Descartes returns to the Platonic dualism (refuted by Aristotle) where the self is defined as the soul or thinking thing (res cogitans) and distinct from the body (res extensa). This statement holds because we can doubt our body but not our self as thought. There is a radical separation between thought and extension (matter). The Cartesian system introduces a new problem: the communication between body and mind, which Descartes attempts to solve with the pineal gland.
The criterion of truth is a rule that tells us when we can be certain of anything. This is implicit in the first rule of his method: an idea is clear when it is presented directly and not derived from others, and distinct when separated from any other idea and presented independently.
The criterion of truth is a formal study drawn from the Cartesian intuition (cogito ergo sum). Cartesian Concepts: Substance is that which does not need anything else to exist; attribute is the essential property of a substance; and mode is what needs a substance to exist.
The Evil Genius hypothesis does not undermine the intuitive thought of the cogito, but it does question whether intuitions are evident as a reality outside the mind. The need for God in Descartes’ system is the fourth truth. It is necessary to ensure the criteria of clarity and distinctness.
Since we have been created by God, who is good and benevolent, this will prevent us from falling into error and being fooled by the Evil Genius. The existence of God is the final and absolute guarantee of the criterion of truth.
The Demonstration of the Existence of God
The truth criterion ensures that clear and distinct thoughts in our mind correspond to things external to us, but this does not mean that we can prove that God exists and does not deceive us. While it does not invalidate the Evil Genius hypothesis, it does make the possibility that anything clearly and distinctly perceived is false less likely.
Cartesian evidence of the existence of God is characterized by the following:
- They stem from the cogito, which is the only certainty for Descartes.
- There can be demonstrations by deduction because it is invalid to doubt our arguments and fallacies.
- The proofs are ultimately intuitive.
Three Proofs of Descartes’ Existence of God
Among the ideas in our mind is the idea of God, understood as “perfect substance.” The idea of God is not adventitious because the senses perceive nothing eternal or infinite, nor is it factitious because the imagination cannot reach these attributes of perfection; therefore, it is innate. Descartes discovers that the subject may be the cause of all other ideas, but not the idea of perfection because this is greater than the individual who thinks.
The perfect cannot be the work of the less perfect; only God as an infinite and real being can cause an infinite idea within the thinking subject.
- Descartes, coinciding with St. Augustine, denies that God is the cause of the subject’s existence; it must be admitted that the subject causes itself. But if we had created ourselves, we would possess all possible qualities. However, since we are finite, imperfect, and limited, we find that we cannot be the cause of our own existence. Therefore, our creator must be a more perfect being, in this case, God.
The existence of God is demonstrated by arguments based on the idea of perfection in thought and the principle of causality.
The third demonstration, called the “Ontological Proof,” was proposed by Anselm of Canterbury. According to Descartes, the essence of a perfect being includes its own existence, and therefore, we cannot think of a perfect being as not existing in the same way that we cannot think of a triangle that does not have three sides. Descartes also uses the Criterion of Truth to guarantee the epistemological proof of the existence of the Perfect Being, with the certainty that the Perfect Being is the creator of the subject. This cancels the Evil Genius Hypothesis because God, in His infinite goodness, prevents us from falling into error.
Furthermore, it ensures that the ideas that the subject perceives clearly and distinctly correspond to reality.