Descartes’ Proofs of God: From Cogito to Certainty
Descartes: Beyond the Cogito
The critical part of Cartesian philosophy concludes after finding the first indubitable truth, the ultimate basis of knowledge: the cogito. From this point begins the constructive or deductive phase, applying the third and fourth rules of the method.
The Thinking Self and the Problem of Solipsism
The first consequence of the cogito is that I am a thinking thing (res cogitans), which possesses ideas. This implies that it is evident that within thought, there are ideas. However, the existence of the object of thought is not immediately apparent.
This leads to the problem of Solipsism: a clear and distinct idea persuades me of the thought itself, but not necessarily of the existence of the object thought about.
Proving God to Overcome Doubt
The second consequence relates to the criterion of certainty. Evidence, derived from clear and distinct ideas, is still potentially undermined by the evil genius hypothesis. If we now want to reconstruct the edifice of knowledge, the most urgent task is to restore confidence in our reasoning by demonstrating the impossibility of such a deceiving god.
Descartes’ Proofs for God’s Existence
Descartes provides three arguments concluding the actual existence of God:
The Ontological Argument
This arises from the careful consideration of the idea of God. Whatever we clearly and distinctly recognize as belonging to the essence of something, necessarily belongs to it. When we conceive an idea, we conceive it with its essential properties: for the idea of a triangle, we conceive it as a figure with three angles and three sides, whose angles sum to 180º. However, real existence is only a possible property of the idea of a triangle. Instead, when discussing the idea of God – the idea of a supremely perfect being – we note that it necessarily implies real existence, as supreme perfection requires the perfection of existence. Just as one cannot think of a mountain without its corresponding valley, human reason cannot think of God except as existing. This argument achieves a key goal: finding an idea that implies the existence of a reality external to the self: God.
The Argument from Infinity
Among the self’s innate ideas is the idea of infinity. This idea must be the effect of some cause. It could not originate from myself, as I recognize myself as finite, limited, and imperfect (my doubting is evidence of this limitation). The idea of infinity within me requires an adequate cause (cause and effect must be proportionate; a cause cannot be less than its effect). This cause can only be an infinite cause, meaning an infinite substance must have produced the idea of an infinite being within me. This infinite substance is God.
The Argument from Self-Causation
When I analyze myself, I find myself finite and imperfect: there is greater perfection in knowing than in doubting. If I had created myself, I would have given myself all the perfections I am capable of conceiving, such as omnipotence, omniscience, etc. Thus, it is clear that I did not create myself, but have been created by the being who possesses those perfections of which I have the idea.
God: Foundation for Certainty and Reality
The existence of God has thus been demonstrated. The Cartesian God is a being endowed with all perfections, including truthfulness.
As a result of these reflections, Descartes concludes that the self is not the only existing reality; another being, God, also exists. Having demonstrated God’s existence, Descartes finds the guarantor of certainty, allowing escape from the solipsism of the self and its ideas, thereby grounding the real world and science.