Course 14 · Apologetics
Arguments for the Existence of God
Study the major philosophical arguments for God’s existence in their classic forms, with the best objections of Hume, Kant and contemporary philosophers.
Overview
This course examines the main philosophical arguments that God exists. It treats each argument as a piece of reasoning with premises that can be examined, not as a slogan. For each argument it asks three questions: how it is stated by its best defenders, what the strongest objections are, and what the argument would show even if it succeeded.
The course follows five families of argument: the ontological argument, which begins from the idea of God; the cosmological arguments, including those from motion, contingency and the beginning of the universe; the teleological arguments, which look to order and fine-tuning; the moral argument; and the problem of divine hiddenness, which is raised against theism and which every defender must face. The historical thinkers Anselm, Aquinas, Leibniz, Hume and Kant are read in their own words or in careful summaries, and the course then moves to contemporary work in philosophy of religion, including the modal ontological argument associated with Alvin Plantinga.
The course does not claim that any of these arguments proves the Christian faith, and it does not claim that they have all failed. Philosophers disagree about each of them, and the course says plainly which questions are settled, which are debated and which depend on commitments that go beyond argument. The arguments, if they work, point to a God of a certain kind, not to the God of any one religion.
By the end you will be able to state each argument in numbered form, explain the standard objections and decide for yourself which argument seems strongest. The independent assignment asks you to evaluate three arguments and to defend one against its best opponents.
Objectives
- State the ontological argument as Anselm gave it and explain the objections of Gaunilo and Kant.
- Distinguish necessary from contingent existence and explain why the distinction matters for several arguments.
- Reconstruct the cosmological arguments of Aquinas and Leibniz, including the principle of sufficient reason.
- Explain the kalam cosmological argument and the main objections to its premises.
- Explain why an infinite regress is thought to be a problem and where that claim is disputed.
- State the teleological and fine-tuning arguments and describe the multiverse and other responses.
- State the moral argument in its main forms and explain the objections from evolution and from moral realism without God.
- Describe the argument from divine hiddenness and the Christian replies to it.
- Summarize the critiques of Hume and Kant and explain what contemporary philosophy of religion has done with them.
- Evaluate an argument for God’s existence fairly, saying what it would show if it succeeded.
Course outline
Module 1 Arguments, Existence and Necessity
Set up the vocabulary used by every argument in the course and learn the difference between what must exist and what merely does.
Topics
- Necessary and contingent existence
- Contemporary philosophy of religion
Lessons
Module 2 The Ontological Argument
Study the argument that tries to move from the idea of God to the existence of God, and the objections it has faced for nine centuries.
Topics
- Ontological argument
- Anselm
- Kant
Lessons
Module 3 Cosmological Arguments
Follow the argument from the world to its cause, in the forms given by Aquinas and Leibniz, and see what each depends on.
Topics
- Cosmological arguments
- Argument from contingency
- Infinite regress
- Aquinas
- Leibniz
Lessons
Module 4 The Kalam Cosmological Argument
Study the argument from the beginning of the universe, its medieval roots and its modern form, and the objections from philosophy and physics.
Topics
- Kalam cosmological argument
Lessons
Module 5 Teleological and Fine-Tuning Arguments
Examine arguments from order, purpose and the conditions required for life, and how Hume and Darwin changed the debate.
Topics
- Teleological argument
- Fine-tuning argument
- Hume
Lessons
Module 6 The Moral Argument and Divine Hiddenness
Study the argument from morality to God and the argument against God from his apparent absence, and see how each is answered.
Topics
- Moral argument
- Divine hiddenness
Lessons
Module 7 Contemporary Modal Arguments and Evaluation
Study the modern revival of the ontological argument, and learn to weigh the arguments against one another.
Topics
- Plantinga and contemporary modal arguments
Lessons
Suggested schedule
| When | Work |
|---|---|
| Week 1 | Module 1: Arguments, Existence and Necessity |
| Week 2 | Module 2: The Ontological Argument |
| Week 3 | Module 3: Cosmological Arguments |
| Week 4 | Module 4: The Kalam Cosmological Argument |
| Week 5 | Module 5: Teleological and Fine-Tuning Arguments |
| Week 6 | Module 6: The Moral Argument and Divine Hiddenness |
| Week 7 | Module 7: Contemporary Modal Arguments and Evaluation |
| Week 8 | Independent assignment and self-assessment |
Readings
Required
- Anselm of Canterbury, Proslogion
Anselm’s short and famous argument for the existence of God. Read the first few chapters slowly.
How to use it: Read chapters 2 to 4 closely. Write Anselm’s argument in numbered steps before looking at any summary.
Read online (Christian Classics Ethereal Library) In the library - Thomas Aquinas, Summa Theologiae I, Q. 2: The Existence of God
The short section containing the ‘Five Ways’. The standard starting point for classical arguments for God.
How to use it: Read the whole article. Identify the premise in each way that the objector is most likely to deny.
Read online (New Advent) In the library - Stanford Encyclopedia of Philosophy, Ontological Arguments
A clear scholarly overview of Anselm, Descartes, Leibniz and Plantinga’s modal version.
How to use it: Read the sections on Anselm, Gaunilo, Kant and the modal versions. Use it to check your numbered reconstruction.
Read online (Stanford Encyclopedia of Philosophy) In the library - Stanford Encyclopedia of Philosophy, Cosmological Argument
Covers the argument from contingency, the kalam argument and the main objections.
How to use it: Read for the distinctions between the kinds of cosmological argument and the principle of sufficient reason.
Read online (Stanford Encyclopedia of Philosophy) In the library - Stanford Encyclopedia of Philosophy, Teleological Arguments for God’s Existence
Design arguments from Aquinas to modern fine-tuning, with objections.
How to use it: Read for the history of design arguments and the responses of Hume and Darwin.
Read online (Stanford Encyclopedia of Philosophy) In the library - Stanford Encyclopedia of Philosophy, Fine-Tuning
A careful scholarly treatment of what fine-tuning claims and what it does not show.
How to use it: Read for a careful statement of the fine-tuning claim and the main objections.
Read online (Stanford Encyclopedia of Philosophy) In the library - Stanford Encyclopedia of Philosophy, Moral Arguments for the Existence of God
Lays out the main moral arguments and the replies to them.
How to use it: Read for the main versions of the moral argument and the objections to each.
Read online (Stanford Encyclopedia of Philosophy) In the library
Recommended
- Stanford Encyclopedia of Philosophy, Hume on Religion
Introduces Hume’s critique of natural theology and miracles.
How to use it: Read for Hume’s critique of natural theology and of miracles.
Read online (Stanford Encyclopedia of Philosophy) In the library - Stanford Encyclopedia of Philosophy, Hiddenness of God
The argument from divine hiddenness and the replies to it.
How to use it: Read for the argument from hiddenness and the main theistic replies.
Read online (Stanford Encyclopedia of Philosophy) In the library - Richard Swinburne, The Existence of God
A rigorous cumulative-case argument for God’s existence. Advanced.
How to use it: A long, careful cumulative case; read selectively for the structure of the argument.
Find in a library or bookstore catalog (Open Library) In the library - William Lane Craig, Reasonable Faith: Christian Truth and Apologetics
A widely read textbook of classical and evidential apologetics.
How to use it: Read the chapters on arguments for God, especially the kalam argument, as a defender’s statement.
Find in a library or bookstore catalog (Open Library) In the library - Alvin Plantinga, God, Freedom, and Evil
The short book that set out the free-will defense against the logical problem of evil.
How to use it: Read the part on the ontological argument for a clear account of the modal version.
Find in a library or bookstore catalog (Open Library) In the library - David Bentley Hart, The Experience of God: Being, Consciousness, Bliss
An argument for the classical understanding of God across religious traditions, written by an Orthodox author.
How to use it: A different approach, arguing from the nature of being, consciousness and bliss, for contrast with the formal arguments.
Find in a library or bookstore catalog (Open Library) In the library - Stanford Encyclopedia of Philosophy, Thomas Aquinas
A scholarly introduction to Aquinas’s life, method and main arguments.
How to use it: Use it for the background to the Five Ways.
Read online (Stanford Encyclopedia of Philosophy) In the library - C. S. Lewis, Mere Christianity
A clear, accessible case for central Christian belief, based on wartime radio talks. A good first book for apologetics.
How to use it: Read Book 1 as a popular form of the moral argument.
Find in a library or bookstore catalog (Open Library) In the library
Passages in the Scripture Study
- Romans 1:20 God’s invisible attributes are seen in what has been made; often cited for natural theology.
- Psalm 19:1 The heavens declare the glory of God.
- Acts 14:17 Paul says God has not left himself without witness, in rain and seasons.
- Acts 17:27 God has made humanity to seek him, though he is not far from each one.
- Romans 2:15 The law written on the heart; cited in moral arguments.
- Exodus 3:14 I AM WHO I AM, a text often connected with God as self-existent being.
- Genesis 1:1 In the beginning God created; read in connection with the kalam argument.
- Hebrews 11:3 Understanding that the universe was formed by the word of God.
- Colossians 1:17 In Christ all things hold together; read with arguments about sustaining cause.
- Isaiah 45:15 Truly you are a God who hides himself; central to reflection on divine hiddenness.
- Psalm 10:1 Why do you hide yourself in times of trouble?
- Jeremiah 29:13 You will find me when you seek me with all your heart.
- Job 38:4 Where were you when I laid the foundation of the earth? Read as a reminder of the limits of human reasoning.
- Psalm 14:1 The fool says in his heart there is no God; read it in context, not as a verdict on every doubter.
- 1 Corinthians 1:21 The world did not know God through wisdom; a caution about what philosophy alone can do.
Independent assignment
Three Arguments, One Defense
- Purpose
- To evaluate three arguments for God’s existence with fairness and care, and to defend one of them against its strongest objections.
- Instructions
- Choose three arguments from the course, each from a different family (for example, one ontological, one cosmological or kalam, and one teleological or moral).
- For each argument, write it out in numbered premises and a conclusion, using the best version you can find. Name the thinker or thinkers you draw from.
- For each argument, write a short account of the strongest objections to it, taken from philosophers who hold them. Restate each so that its defenders would accept your summary.
- For each argument, say what it would show if it succeeded. Be specific: a first cause, a necessary being, a designer, a moral lawgiver, and whether any of these would be the God of the Christian faith.
- Rank the three arguments in order of strength, giving reasons that refer to particular premises, not to a general impression.
- Choose one of the three and write a defense of it. State the two or three strongest objections, then reply to each honestly: say whether you deny a premise, question the inference, or accept the point and limit the conclusion.
- Address one objection that you cannot answer fully, and say what you would need to learn to answer it.
- Add a paragraph on divine hiddenness: how it bears on your chosen argument and how a defender might reply.
- Close with a paragraph on how confident you are in each of the three arguments, what each argument fails to show, and how you would explain these limits to a skeptical friend.
- Required sources
- At least four of the required readings.
- At least one primary work (Anselm, Aquinas, Leibniz, Hume or Kant, or a contemporary philosopher’s own paper) and at least one source that argues against each of your three arguments.
- At least four of the Scripture passages listed for this course, if you refer to Scripture.
- Length and scope
- About 3,500 to 5,000 words, or twelve to sixteen pages, including the numbered arguments. Keep it in your own notebook or document. Do not send it anywhere.
- Questions to address
- Which premise of each argument carries the most weight?
- Which objection is the most serious, and does it defeat the argument or only weaken it?
- What does each argument establish about God, and what does it leave open?
- Would a thoughtful atheist and a thoughtful theist agree with my summary of the objections?
- How would my evaluation change if one premise turned out to be false?
- Expected output
- A written evaluation of three arguments, with numbered reconstructions, fairly stated objections, a ranking with reasons, and a full defense of one argument against its strongest critics.
- How it will be evaluated
- Each argument is reconstructed accurately and in its best form.
- Objections are drawn from their own defenders and stated fairly.
- The claim about what each argument would show is precise and not exaggerated.
- The ranking refers to particular premises and reasons.
- The defense replies to the objection actually made, and admits what is left unresolved.
- The conclusion distinguishes proof, probability and personal conviction.
- Common mistakes to avoid
- Treating an argument for a first cause as if it proved the Trinity or the Bible.
- Attacking a popular or simplified version of an argument instead of the one the best philosophers defend.
- Citing Hume or Kant from memory without reading them or a reliable summary.
- Dismissing an objection because the objector is an atheist, or accepting it for the same reason.
- Overstating the strength of the conclusion.
Knowledge check and self-assessment
State Anselm’s ontological argument and give one objection.
Anselm defined God as a being than which nothing greater can be thought. He argued that if such a being existed only in the mind, a greater one could be thought, namely one that also exists in reality; so God must exist in reality. Gaunilo replied that the same reasoning would prove a perfect island. Kant objected that existence is not a property that adds to a concept. Anselm’s defenders reply that the argument applies only to a being of unsurpassable greatness.
What is the difference between necessary and contingent existence?
A contingent thing might not have existed: it depends on other things and could have failed to be. A necessary being, if there is one, could not fail to exist and does not depend on anything else. Many arguments claim that contingent things need an explanation and that the explanation ends in a necessary being. Critics question whether the idea of a necessary being is coherent or whether the universe itself could be necessary.
What is the principle of sufficient reason, and why does Leibniz’s argument depend on it?
The principle says that everything that exists has an explanation for why it exists rather than not. Leibniz argued that the universe is a collection of contingent things, so it needs an explanation outside itself, in a necessary being. The argument stands or falls with the principle. Critics say that the world may simply be a brute fact, or that the principle, if applied to everything, leads to troubling conclusions about necessity and freedom.
Why do cosmological arguments reject an infinite regress?
In Aquinas’s causal chains, each member acts only because another is acting now, so a series with no first member would have no source of power at all, like links that hang from nothing. This differs from a chain stretching back in time. Critics reply that an infinite series could be self-explanatory as a whole, or that the argument assumes what it needs to show. The kalam argument gives a different reason, based on the impossibility of an actual infinite.
State the kalam cosmological argument and name the premise most often disputed.
Its form is: whatever begins to exist has a cause; the universe began to exist; therefore the universe has a cause. Defenders support the second premise with philosophical arguments against an actual infinite past and with the standard Big Bang model. Critics dispute the first premise, citing quantum events, and the second, citing models without a first moment. Even if sound, the argument shows a cause beyond the universe, not the Christian God as such.
What did Hume and Kant each criticize in the arguments for God?
Hume questioned the design argument, saying that we have no experience of universes being made and that the analogy between nature and a machine is weak. He also questioned the idea of a necessary being. Kant argued that the ontological argument wrongly treats existence as a property, and that reason loses its way when it reaches beyond experience. Both critiques remain influential, though many contemporary philosophers think they do not defeat all versions of the arguments.
What is the fine-tuning argument, and what is the multiverse reply?
The argument notes that the basic constants and conditions of physics fall within narrow ranges that allow life, and it holds that this is more likely if the universe was designed than if it arose by chance. The multiverse reply proposes that there are many universes with varying constants, so a life-permitting one is not surprising. Critics of that reply say it is speculative and may need its own fine-tuning. Whether fine-tuning needs explanation at all is itself debated.
What is the argument from divine hiddenness, and how might a Christian respond?
J. L. Schellenberg argued that a loving God would make himself evident to every open-minded person, yet some sincerely seek God and find nothing, so God probably does not exist. Christians reply in several ways: God may value free and trusting response, which overwhelming evidence could undermine; God may be present in ways not recognized; or human resistance may play a part. Critics think these replies do not fit every case of sincere seeking.
Judge your own progress
- When you finish the modules, answer the knowledge questions from memory, without notes. Aim for 70 percent or better; if you score lower, reread the relevant module and try again.
- Write your evaluation of three arguments (the independent assignment). Wait three days, reread it, and mark every place where an objection is stated unfairly or a premise is left implicit.
- Check your work against the evaluation criteria in the assignment. Rate each criterion as strong, adequate or weak and write one sentence on how you would improve each weak one.
- Return to the key ideas after 1 day, 7 days, 30 days and 90 days. At each point, state one argument in numbered form from memory and give its best objection.
- You can state each of the major arguments in numbered form and name the thinkers who developed it.
- You can state the strongest objections to each argument in terms its defenders would accept.
- You can say precisely what each argument would and would not show about God.