How did Descartes formulate the ontological argument in the "Meditations," and what is the difference between his formulation and Anselm's?

In his "Meditations on First Philosophy" (1641), René Descartes presented a new formulation of the ontological argument that differs fundamentally from Anselm of Canterbury's formulation that preceded it by six centuries. Understanding the difference between these two formulations is necessary for evaluating the strengths and weaknesses of each.

Inadequate Responses to Be Avoided

From some believers:

"Descartes merely repeated Anselm's argument in different language." This is a historical and philosophical error. Descartes was not familiar with Anselm's argument when he formulated his own (he discovered this later through his correspondence with Mersenne). More importantly: the logical structure of the two arguments is radically different, and criticism that applies to one may not apply to the other.

"All ontological arguments prove God's existence conclusively." This is an overstatement. Even contemporary proponents of the ontological argument (Plantinga, Hartshorne) acknowledge that it depends on debatable metaphysical premises. Claiming it is a "conclusive proof" weakens the faith position rather than strengthening it.

From some critics:

"Kant destroyed the ontological argument definitively." This is a common exaggeration. Kant's criticism applies to certain formulations (especially the Cartesian one), but contemporary formulations (Modal Ontological Argument) transcend his criticism. The claim of "definitive destruction" ignores the development of philosophical debate.

"The ontological argument is merely a linguistic trick." This is a harmful reduction. The argument raises deep metaphysical questions about the nature of existence, necessity, and possibility. Even philosophers who reject it (Russell, Quine) acknowledge that it reveals serious philosophical problems.

Why These Responses Are Inadequate

They fail to distinguish between different formulations and to understand the precise logical structure of each formulation. Serious evaluation requires analyzing each formulation in its philosophical context.

Anselm's Formulation (Proslogion, 1078)

Anselm begins with a definition: God is "that than which nothing greater can be conceived" (id quo maius cogitari non potest). The argument proceeds as follows:

1. Even the fool (insipiens) who denies God's existence understands this definition
2. What is understood exists in the mind at least
3. But existence in reality is greater than existence in the mind only
4. If "that than which nothing greater can be conceived" existed only in the mind, one could conceive of something greater (existing in reality as well)
5. This is a contradiction
6. Therefore "that than which nothing greater can be conceived" exists in reality

The structure here is: reductio ad absurdum — assuming the opposite of what is required leads to contradiction.

Contemporary criticism by Gaunilo: The same logic could be applied to the "perfect island" — which is absurd. Anselm replied that the argument applies only to the necessary being, not to possible beings like islands.

Descartes' Formulation (Fifth Meditation)

Descartes takes a completely different approach. He does not begin with "the greatest conceivable being," but from analyzing the idea of God as an "infinitely perfect being":

1. I have a clear and distinct idea of God as an infinitely perfect being
2. Infinite perfection includes all perfections
3. Existence is a perfection (it is a lack for something not to exist)
4. Therefore existence is included in God's essence
5. Separating existence from God is like separating the sum of angles of a triangle = 180° from the triangle
6. Therefore God exists necessarily

The structure here is: conceptual analysis — existence is part of God's essence, just as the properties of a triangle are part of its essence.

Fundamental Differences Between the Two Formulations

First Difference: Starting Point
- Anselm: relative concept ("greater than")
- Descartes: absolute concept ("infinite perfection")

This is an important difference. Anselm's argument depends on comparison (existence in reality > existence in mind). Descartes' argument depends on direct conceptual analysis.

Second Difference: Nature of Reasoning
- Anselm: proof by contradiction (reductio)
- Descartes: direct deduction from analysis

Anselm shows that denying God's existence leads to contradiction. Descartes shows that God's existence is directly included in his concept.

Third Difference: Role of Human Thought
- Anselm: even one who denies God must fall into contradiction
- Descartes: one who has a clear idea of God sees his existence as necessary

Anselm tries to bind the denier. Descartes relies on "clear and distinct ideas" in his philosophical method.

Fourth Difference: Relation to the Philosophical System
- Anselm: relatively independent argument
- Descartes: part of an integrated system including the cogito and dualism

For Descartes, the ontological argument is connected to his theory of innate ideas and his need to guarantee the truth of clear perceptions.

Different Strengths and Weaknesses

Anselm's strength: logical simplicity and elegance. Does not need a complex philosophical system.

Anselm's weakness: the transition from "conception" to "existence" seems suspect. Kant's criticism about existence as "not a real predicate" applies directly.

Descartes' strength: the close connection between essence and existence in the case of the infinite being seems stronger than mere comparison.

Descartes' weakness: dependence on "clear and distinct ideas" and the theory of innate ideas. One who does not accept the Cartesian framework will not accept the argument.

Kantian Criticism and Its Different Impact

Kant's famous criticism — "existence is not a real predicate" — affects the two formulations differently:

Against Descartes: The criticism is direct. Descartes explicitly treats existence as a perfection/predicate. Kant says: existence is not a quality added to essence, but the "position" of the thing in reality. 100 conceived talers = 100 existing talers in terms of conceptual content.

Against Anselm: The criticism is less direct. Anselm does not explicitly say that existence is a predicate, but says that "existence in reality" makes the thing "greater." Contemporary supporters of Anselm (Malcolm, Hartshorne) developed readings that avoid Kant's criticism.

Contemporary Developments

Contemporary formulations (Modal Ontological Argument in Plantinga) are closer to Anselm's spirit than to Descartes':

1. It is possible for a maximally great necessary being to exist
2. If it is possible for a necessary being to exist, it exists in some possible world
3. A necessary being, if it exists in one possible world, exists in all worlds
4. Therefore the maximally great necessary being exists in our world

This formulation avoids the problem of "existence as predicate" but depends on accepting the first premise, which is controversial.

Where We Stand Today in This Debate

There is no philosophical consensus. The ontological argument remains one of the most controversial arguments:

- Believing philosophers of religion are divided: some (Plantinga, van Inwagen) defend it, some (Swinburne, Craig) reject it
- Atheist philosophers generally reject it, but to varying degrees: some (Oppy, Sobel) respect its philosophical complexity
- The middle position (methodological agnosticism): the argument reveals deep metaphysical questions more than it resolves them

The Methodological Lesson

The difference between Anselm's and Descartes' formulations shows that "the ontological argument" is not one argument but a family of arguments. Precise evaluation requires analyzing each formulation with its own tools. This applies to all classical philosophical arguments — the devil (and the angel) is in the details.

For Advanced Reading

- Advanced level: modal logic and the contemporary ontological argument in Plantinga
- Advanced level: Oppy's criticism of the modal ontological argument and van Inwagen's replies
- Descartes, Meditations on First Philosophy (Fifth Meditation)
- Brian Davies & Brian Leftow (eds.), The Cambridge Companion to Anselm (2004)
- Graham Oppy, Ontological Arguments (Stanford Encyclopedia of Philosophy)
- "Ontological Arguments Through History" page on the website