Ontological Argument Descartes

Formulation of Descartes’ Ontological Argument

René Descartes presents his ontological argument primarily in Meditations on First Philosophy (Meditation V), as part of his broader project of establishing certain knowledge on the basis of clear and distinct ideas. The argument is meant to show that God’s existence can be known a priori, purely from reflection on the idea of God, without appeal to empirical evidence.

Descartes defines God as a “supremely perfect being” possessing all perfections (such as omniscience, omnipotence, and moral perfection). He claims that existence is among these perfections or is at least inseparable from the essence of such a being. Just as the essence of a triangle includes the fact that its interior angles sum to 180 degrees, the essence of a supremely perfect being includes existence.

The argument can be summarized as follows:

• From introspection, I find in my mind the idea of God as a supremely perfect being.
• A supremely perfect being must contain every perfection.
• Existence is either a perfection or necessarily follows from supreme perfection.
• Therefore, a supremely perfect being cannot lack existence.
• Hence, God necessarily exists.

Descartes emphasizes that this is not an empirical claim, but a matter of conceptual necessity: once one grasps the idea of a supremely perfect being, one sees that such a being cannot be conceived as non-existent without contradiction, in the same way that a mountain cannot be thought without a valley, or a triangle without its defining properties.

Relation to Anselm and Clear and Distinct Ideas

Descartes’ ontological argument is historically linked to, but distinct from, Anselm’s earlier ontological argument. Both begin from the concept of God and attempt to derive God’s existence, but their emphases differ:

• Anselm focuses on God as “that than which nothing greater can be conceived,” arguing that a being which exists in reality is greater than one that exists only in the understanding.
• Descartes concentrates on God’s essence as supremely perfect, and the claim that existence belongs to that essence just as necessarily as certain properties belong to mathematical objects.

For Descartes, the ontological argument is closely connected to his theory of clear and distinct perception. He holds that:

1. Whatever is perceived clearly and distinctly is true.
2. The idea of God as a supremely perfect being is a clear and distinct idea.
3. From this clear and distinct idea, it follows that God exists.

The ontological argument thus plays a role within Descartes’ broader epistemological strategy. Once God’s existence is established, God’s non-deceptive nature is used to secure the reliability of clear and distinct perceptions in general, helping to ground mathematical and scientific knowledge.

Major Objections and Critical Responses

Descartes’ formulation has been the focus of sustained criticism. Several major lines of objection are commonly discussed:

1. Existence as a Predicate (Kantian Objection)
Immanuel Kant famously argued that “existence is not a real predicate”—that is, not a property that adds to the concept of a thing. To say that something exists, according to Kant, does not describe a new attribute it has, but rather affirms that a concept is instantiated. On this view, Descartes cannot legitimately treat existence as a perfection in the same way as wisdom or power. Critics using this line of thought contend that the argument illegitimately builds existence into the definition of God and then “discovers” it there.

2. The Parody or “Perfect Island” Objections
Following similar criticisms of Anselm, some philosophers have proposed parody arguments: for example, defining a “most perfect island” and then arguing that existence is one of its perfections, so it must exist. Proponents of the ontological argument respond that only necessary beings are relevant; islands and other contingent objects cannot be coherently defined as necessary. The dispute then shifts to whether the concept of a necessary, supremely perfect being is itself coherent and unique.

3. Questioning Clear and Distinct Ideas
Descartes’ argument presupposes that the idea of God as a supremely perfect being is grasped clearly and distinctly and that such clarity is a guarantee of truth. Critics challenge both assumptions:

• They argue that the concept of a maximally perfect being might be vague or internally problematic.
• They also question whether a subjective feeling of clarity is a reliable indicator of metaphysical necessity.

4. Conceptual vs. Ontological Necessity
Some philosophers grant that, given a certain definition of “God,” it may be analytically true that “if God exists, then God exists necessarily.” However, they deny that from this conceptual truth one can infer that there is any corresponding reality. On this view, the ontological argument may show something about the concept of God but not about what actually exists.

Despite these criticisms, defenders of Descartes’ argument attempt to refine it using more sophisticated modal logic, arguing that if the existence of a necessary being is possible, then such a being must exist in all possible worlds, including the actual one. Whether these developments preserve Descartes’ original intentions or significantly transform the argument remains contested.

Philosophical Significance

Descartes’ ontological argument remains a central case study in the philosophy of religion and metaphysics. It is important for several reasons:

• It illustrates the ambitions of rationalist epistemology, attempting to derive substantive truths about reality from pure reason and the analysis of ideas.
• It has shaped later debates about the nature of existence, necessity, and the legitimacy of a priori arguments for the existence of God.
• It continues to provoke methodological questions about how far one can travel from conceptual analysis to claims about what there is.

The argument is generally regarded as controversial rather than decisively refuted or established. It continues to be discussed both in historical scholarship on Descartes and in contemporary analytic philosophy, where modern modal versions of the ontological argument draw inspiration, in part, from Descartes’ insistence that necessary existence belongs to the essence of a supremely perfect being.