In the Meditations, Descartes aims to build a foundation for the certainty and truths of our knowledge. In Meditation Four, he demonstrates the Truth Rule: what we perceive clearly and distinctly is true. In this paper, I will present his arguments by analyzing the structure and reasoning of his propositions. I will begin by defining and clarifying necessary terminology, such as what he means by clearly perceiving. Next, I will state and formalize the explicit and implicit assumptions and the major propositions central to his arguments. I will explore how Descartes justifies these propositions and derives his conclusions from the established assumptions. Finally, I will evaluate the seeming circularity in the Truth Rule justification, arguing that it is not necessarily circular.
First, I will clarify terms that could be interpreted ambiguously or differ in the Meditations. This will include correcting potential misunderstandings and highlighting Descartes' specific distinctions between these concepts.
According to Descartes, everything we perceive through the senses is a clear perception because “the ideas, or thoughts, of such things appeared before my mind” (35). Thus, perception is clear when it is apparent to our conscious awareness as ideas presented in our mind, not in the objects themselves.
Descartes does not define a distinct perception, but I understand it in the following way. A perception is distinct if it is separate from all other perceptions and contains within itself only what appears to the mind.
Since clearness and distinctness serve as conditions for truth, we must be able to determine the scope of subjects for which an assessment of truth is applicable. Descartes distinguishes between different types of thoughts: those that represent “images of things” (ideas), such as my thought of a desk, and those that are concerning and attached to an object of that thought, some of which are called “volition or emotions, while others are called judgments” (37). Ideas, when considered alone, cannot be false because they are only reflections within the mind, regardless of their depiction of objects. Thus, only when we make judgments—evaluating the correspondence of our concepts with external reality—can we discuss whether our assertion and thoughts about an idea accurately reflect the external world or the nature of things.
In his Truth Rule, Descartes relies on and establishes the existence of an infinitely Good God. Descartes’ idea of God is a being that is perfect in every sense: “eternal, infinite, <immutable>, omniscient, omnipotent and the creator of all things that exist apart from him” (40). While presenting Descartes’ arguments for God, I will draw out the underlying assumption in each of his assertions. I begin with Descartes' examination of the cause-and-effect relationship.
Lemma 1: Everything must have a reason, cause, or explanation for its existence or occurrence.
Descartes neither explicitly states the lemma nor the reasoning, but he repeatedly uses it as an underlying assumption. This premise arises from the intuitively implausible notion that something could arise from nothing. Our efforts to comprehend and make sense of the universe inherently reject the idea of an uncaused effect, as a lack of causality fundamentally undermines our attempt at an explanation. I think that we form ideas and make judgments to understand the world. This inseparability of judgments as a method of understanding leads us to believe that everything must have a cause. A similar line of reasoning leads to the Causal Principle.
Proposition 1 (Causal Principle): “There must be at least as much <reality> in the efficient and total cause as in the effects of that cause” (40).
If an effect were greater than its origin in terms of actuality or perfection, then it would suggest that this additional reality came into existence without a corresponding cause, which violates Lemma 1. Thus, the cause must possess the essential characteristics or levels of reality to bring about the effect. A related claim to causality is the impossibility of infinitely propagating back in a causal chain as stated in the following proposition.
Proposition 2: Infinite regresses are not possible (42).
Lemma 1 leads Descartes to reject the prospect of an unending chain in which one idea causes another ad infinitum. If an unending chain were possible, an infinite regress of causes would violate Lemma 1 because it would leave the existence of any idea without a definitive, ultimate cause. A lack of ultimate cause contradicts Lemma 1 in that everything must have a clear and adequate cause or reason for its existence. Then by our certainty of existence and Propositions 1 and 2, our existence requires an original cause. As Descartes further examines, only God could have been the source of our existence.
Conclusion 1: Only God could be the source of my existence, thus proving God's existence (50).
If I created myself, I would be perfect because as a thinking thing, it is more challenging to create oneself from nothing than to acquire new knowledge. My lack of certain knowledge is an imperfection that indicates that I am not my creator. The causal principle suggests that a higher entity is responsible for my existence. The necessity to avoid infinite regress and the idea of a perfect being imply that this ultimate creator, embodying the concept of perfection as a perfection, must itself be perfect (50). Therefore, this creator is God, who embodies all perfections, including existence. It also follows that God lacks the power to deceive us because the intent to deceive is a weakness, which a perfect being cannot have (53). From this, we can conclude the truth rule.
Conclusion 2 (Provisional): What I perceive clearly and distinctly is true.
By Conclusion 1, I owe God my existence and all my attributes, including my faculty of judgment. Since God cannot deceive me, “he surely did not give me the kind of faculty which would ever enable me to go wrong while using it correctly” (53). This lays the groundwork for the Truth Rule by confirming the reliability of our clear and distinct judgments as truths.
However, this assertion raises questions when considering the errors and mistakes we often encounter in our judgments. If our provisional Truth Rule suggests that our clear and distinct perceptions are infallible, then how can we account for these errors? I will now examine Descartes’ rationale for God allowing us limited knowledge and the tendency to make mistakes.
As God’s creation, the causal principle asserts that humans are intermediates between God and nothingness. We possess capabilities and deficiencies, including the lack of an infinite true judgment faculty (54). This limitation also implies that God’s reason for our partial knowledge remains uncertain to us; however, given God's goodness, our incompleteness must contribute to the perfection of the universe. The root of our mistakes lies in the mismatch between our finite knowledge and infinite will (58).
The cause of our mistakes is neither our will—given to us by God and perfect in its capacity—nor our understanding, which, being divine in origin, is correct in what it does comprehend. We make mistakes because the “scope of the will is wider than that of the intellect; but instead of restricting it within the same limits, I extend its use to matters which I do not understand” (58). By applying our will to concepts beyond our understanding, we deviate from truth and goodness, revealing the origin of error and sin in the misapplication of our will beyond our understanding.
This pinpointing of error allows Descartes to conclude that not all is uncertain. Because we have a perfect capacity to understand, the clarity in understanding compels us toward acknowledging its truth, directing our sometimes misguided will. Hence, to circumvent error, Descartes advises to “refrain from making a judgment in cases where [we] do not perceive the truth with sufficient clarity and distinctness” (59). This approach avoids error, and we conclude our truth rule.
Conclusion 2 (Truth Rule): What I perceive clearly and distinctly is true.
I will now address the circular nature of Descartes’ proof of the Truth Rule. Descartes relies on the existence of a perfect God. As I have mentioned in Lemma 1, the axioms of causal relationships can only be justified through their clarity in our understanding. Without it, the core propositions and, subsequently, God’s existence, cannot be claimed. Thus, the implicit dependence on the Truth Rule for God, who then guarantees the Truth Rule, challenges the validity of his argument.
The dependence, however, does not necessarily imply that the Truth Rule is circular. The circularity stems from Descartes’ reliance on the Truth Rule to justify the existence of a perfect God. I observe that a valid proof of God does not necessarily require the Truth Rule. Descartes indicates in the Dedicatory Letter to the Sorbonne that his argument appeals to those without prior faith in God. Consequently, for individuals already possessing faith in God or who accept an alternate proof of God's existence, the Truth Rule maintains its validity independently of this circular reasoning.
This perspective suggests that the apparent circularity in the proof may not undermine the Truth Rule but rather highlights the specific challenges in presenting a logical proof of God. Furthermore, for those who already believe in God, Descartes' argument may serve as a reflective process, where the understanding of one reinforces the other in a mutually supportive but not circular manner. This reflective process suggests a deepening of understanding and marks a clear starting point instead of a loop. Therefore, though Descartes’ full proof of God and the Truth Rule is circular, the Truth Rule in isolation is not.