Overview
The ontological argument is unique among arguments for God's existence because it attempts to prove God exists through reason alone, without appealing to experience or empirical evidence. It argues that God's existence follows logically from the very concept or definition of God.
Distinctive Features
- A priori: Based on reason alone, not experience
- Definitional: Starts with the concept or definition of God
- Necessary existence: Concludes God must exist necessarily
- Purely logical: No empirical premises required
Historical Significance
The ontological argument has fascinated philosophers for nearly a thousand years, generating intense debate about the relationship between concepts, definitions, and existence. Even critics often find it intellectually compelling despite rejecting it.
Anselm's Original Argument
Saint Anselm of Canterbury (1033-1109) first formulated the ontological argument in his work Proslogion.
God is "that than which nothing greater can be conceived" (aliquid quo nihil maius cogitari possit).
Anselm's Reasoning
- God is that than which nothing greater can be conceived
- This concept exists in the understanding (even the fool understands it)
- It is greater to exist in reality than only in the understanding
- If God existed only in the understanding, we could conceive something greater (the same being existing in reality)
- But this contradicts the definition of God as the greatest conceivable being
- Therefore, God must exist in reality
The Second Argument
Anselm also offered a second argument focusing on necessary existence:
Something that cannot be conceived not to exist is greater than something that can be conceived not to exist. Therefore, God (the greatest conceivable being) cannot be conceived not to exist—God exists necessarily.
Gaunilo's Objection
Contemporary monk Gaunilo objected with his "perfect island" parody: by Anselm's logic, we could prove the existence of a perfect island that than which no greater island can be conceived. Anselm replied that the argument only works for a maximally great being.
Descartes' Version
René Descartes (1596-1650) reformulated the ontological argument in terms of perfection and necessary existence.
1. God is a supremely perfect being
2. Existence is a perfection
3. Therefore, God exists
The Geometric Method
Descartes compared his argument to geometric proofs:
- Just as having three angles equaling 180° belongs to the essence of a triangle
- Existence belongs to the essence of a supremely perfect being
- We can no more separate existence from God's essence than we can separate geometric properties from shapes
Necessary vs. Contingent Existence
Descartes' Innovation
Descartes emphasized that God's existence is not contingent (like created things) but necessary—God cannot fail to exist because existence is part of the divine essence, like how having three sides is part of the essence of a triangle.
Modal Ontological Arguments
Contemporary philosophers have formulated sophisticated versions using modal logic (the logic of possibility and necessity).
Plantinga's Version
1. It is possible that a maximally great being exists
2. If it's possible that a maximally great being exists, then a maximally great being exists in some possible world
3. If a maximally great being exists in some possible world, then it exists in every possible world
4. If a maximally great being exists in every possible world, then it exists in the actual world
5. Therefore, a maximally great being exists in the actual world
Key Concepts
- Maximal greatness: Having maximal excellence in every possible world
- Maximal excellence: Omnipotence, omniscience, moral perfection
- Necessary existence: Existing in all possible worlds
- S5 modal logic: If something is possibly necessary, then it is necessary
The Crucial Premise
The modal argument's strength depends entirely on premise 1: whether it's possible that a maximally great being exists. Critics argue this premise is questionable and that the argument proves at most that if God's existence is possible, then God exists necessarily.
Major Criticisms
The ontological argument has faced persistent and influential criticisms throughout its history.
Kant's Critique
Immanuel Kant offered perhaps the most famous criticism:
Kant argued that existence is not a real predicate or property that can be added to a concept. Saying something exists doesn't add any content to the concept—it merely asserts that the concept is instantiated in reality.
Contemporary Criticisms
- Parody arguments: The logic seems to prove too much (perfect islands, etc.)
- Incoherent concept: The concept of God may be self-contradictory
- Question-begging: The argument assumes what it tries to prove
- Modal collapse: Some versions lead to fatalism
The Characterization Problem
Defining Greatness
Critics question whether we can coherently define "maximal greatness" or "perfection." Different conceptions of divine perfection might be incompatible, and some alleged perfections may be impossible to maximize.
Gödel's Ontological Proof
Logician Kurt Gödel developed a highly technical modal ontological argument using formal logic.
Gödel's Axioms
- Axiom 1: Either a property or its negation is positive
- Axiom 2: A property necessarily implied by a positive property is positive
- Axiom 3: The property of being God-like is positive
- Axiom 4: If a property is positive, then it is necessarily positive
- Axiom 5: Necessary existence is positive
Something is God-like if and only if it possesses all positive properties.
The Proof Structure
From these axioms, Gödel derives:
- Positive properties are possibly exemplified
- The property of being God-like is possibly exemplified
- Necessary existence is God-like
- Therefore, God necessarily exists
Technical Concerns
While mathematically sophisticated, Gödel's proof faces questions about the coherence of his axioms and whether "positive properties" can be defined without circularity.
Assessment
The ontological argument remains one of the most debated and philosophically rich arguments in the history of thought.
Enduring Appeal
- Purely rational approach to proving God's existence
- Ingenious attempt to derive existence from essence
- Continues to generate sophisticated philosophical discussion
- Explores fundamental questions about existence and necessity
Persistent Problems
- Kant's criticism remains influential
- Parody arguments suggest the logic proves too much
- Questions about the coherence of maximal greatness
- Disputed intuitions about possibility and necessity
Contemporary Status
Current Debate
While few philosophers are convinced by ontological arguments, they continue to be refined and debated. The arguments have contributed significantly to developments in modal logic, philosophy of language, and metaphysics, even if they haven't settled the question of God's existence.
Whether or not they succeed in proving God's existence, ontological arguments have deepened our understanding of concepts, existence, necessity, and the relationship between logic and reality.