The ontological argument

The ontological argument is a priori and deductive: it tries to prove God from the concept of God alone, without appealing to experience of the world.

• Anselm (Proslogion): God is "that than which nothing greater can be conceived". A being that exists in reality is greater than one existing only in the mind, so the greatest conceivable being must exist in reality — otherwise we could conceive of something greater.
• Anselm's second form: God has necessary existence — a being that cannot fail to exist is greater than a contingent one.
• Descartes: existence is a perfection, and God is a supremely perfect being, so existence belongs to God's essence as three angles belong to a triangle.

Gaunilo's reply ("on behalf of the fool"): the same logic would prove the most perfect island must exist — a reductio Anselm rejected, since only God has necessary existence.

Kant: existence is not a predicate

Kant's decisive objection: existence is not a predicate (not a real property that adds to a concept). Saying "God exists" does not describe God the way "God is powerful" does — it asserts that the concept is instantiated.

So you cannot define God into existence: a "hundred real thalers" contain no more coins than a "hundred possible thalers". This undercuts both Anselm and Descartes.

Norman Malcolm partly rescued Anselm's second form, arguing necessary existence is a coherent property; critics reply this still trades on treating existence as a predicate.

Whose objection?

Cosmological arguments

Cosmological arguments are a posteriori: they start from a fact about the world (that things exist, move, change) and reason to a first cause.

• Aquinas' Five Ways — the first three are cosmological: the unmoved mover (motion needs a first mover), uncaused cause (a series of efficient causes needs a first cause), and contingency and necessity (if everything were contingent, at some point nothing would have existed; so there must be a necessary being).
• Kalam argument (revived by William Lane Craig): whatever begins to exist has a cause; the universe began to exist; therefore the universe has a cause. Craig rejects an actual infinite regress of past events.

Key move: Aquinas denies an infinite regress of essentially-ordered causes and calls the terminus "God".

Challenges to the cosmological argument

• Hume: the causal principle is not logically necessary; and from a finite effect we cannot infer an infinite cause. Why not the universe itself as the necessary/brute fact?
• Russell (in his debate with Copleston): "the universe is just there, and that's all" — the demand for a cause of the whole series may be a fallacy of composition.
• Defence: Leibniz' principle of sufficient reason — even a necessary being is needed to explain why there is something rather than nothing.

Which way is which?

Teleological (design) arguments

Teleological arguments reason from apparent order, regularity and purpose in nature to a designer.

• Paley's watch: finding a watch on a heath, its intricate parts arranged for a purpose imply a watchmaker. Nature (e.g. the eye) shows the same purposive design, so implies a divine designer. This is design qua purpose and qua regularity.
• Aquinas' Fifth Way: things without intelligence (like an arrow) act toward an end only if directed by an intelligent being.
• Modern versions appeal to cosmic fine-tuning (the anthropic principle).

Hume's objections to design

Hume (in the Dialogues Concerning Natural Religion) pressed several objections, mostly voiced through Philo:

• The analogy is weak: the universe is not much like a machine; it might be more like a growing organism or vegetable.
• We have no other universes to compare, so we cannot say this one is designed.
• Even if designed, we cannot infer a single, infinite, perfect or benevolent designer — perhaps many gods, or an apprentice deity.
• Epicurean hypothesis: given infinite time, random order can arise unaided (anticipating natural selection).

Darwin later gave a naturalistic account of apparent design; Dawkins ("the blind watchmaker") argues natural selection removes the need for Paley's designer.

Whose watch?

Weighing the arguments

Examiners reward candidates who evaluate, not just describe:

• Do a priori proofs (ontological) ever establish real existence, or only relations of ideas?
• Does the cosmological argument commit the fallacy of composition, or does the principle of sufficient reason survive Hume and Russell?
• Does evolutionary biology defeat design, or merely relocate the question to the laws and constants that make evolution possible?
• Are these best read as proofs, or as cumulative pointers that make theism reasonable (Swinburne's inductive, probabilistic approach)?

Sort each argument by type

Tap a claim, then drop it under a priori or a posteriori.

Match scholar to move

Tap a description, then the scholar or idea it belongs to.

The big ideas to hold together

You can now state each argument, name its key thinkers, and deploy the standard objections. Press Finish to see your score.