Responding to atheism — the philosophical case for God

Atheism is often presented as the neutral position — the absence of a claim, requiring no defence. It is not.

An atheist worldview asserts that the universe came from nothing or has always existed; that life self-assembled from non-life; that consciousness arose from unconscious matter; that reasoning is a by-product of processes not aimed at truth; and that morality is an evolved preference with no objective standing.

Those are substantial claims. They should be examined with the same rigour any Christian claim receives. And the examination should be conducted without contempt, because the goal is a person, not a scoreline.

The kalām cosmological argument

Ancient in origin — developed by medieval Islamic philosophers — and revived in contemporary philosophy largely by William Lane Craig. Its strength is its brevity.

Premise 1: Whatever begins to exist has a cause.

Denying this is more costly than it looks. Things do not simply pop into being uncaused; if they did, we should wonder why it never happens to horses or bicycles. This is not merely a habit of mind — it is the foundation of all scientific investigation.

Premise 2: The universe began to exist.

This is the premise that changed in the twentieth century. For most of history the scientific consensus was an eternal universe; it was Christians who argued for a beginning. Then came Hubble's expansion, the Big Bang model, the cosmic microwave background, and the Borde–Guth–Vilenkin theorem (2003), which shows that any universe on average expanding must have a past boundary.

Philosophically, an actually infinite past also generates paradoxes — if an infinite number of days had to elapse before today, today would never arrive.

Conclusion: Therefore the universe has a cause.

Then ask what such a cause must be like. It caused space, so it is not spatial. It caused time, so it is timeless. It caused matter, so it is immaterial. It is enormously powerful. And it must be personal — because an impersonal set of eternal conditions would produce an eternal effect, whereas a beginning in time requires a will that acts.

Timeless, spaceless, immaterial, immensely powerful, personal. That is not a proof of the Christian God specifically. It is a great deal more than nothing.

The fine-tuning argument

The physical constants that govern the universe fall within extraordinarily narrow ranges for life to be possible.

• The cosmological constant is fine-tuned to something on the order of one part in 10¹²⁰.
• The strong nuclear force: alter it by a few per cent and either no hydrogen exists, or no heavy elements do.
• The ratio of electrons to protons, the expansion rate, the mass difference between neutron and proton — the list runs long.

Roger Penrose calculated the odds of the universe's initial low-entropy state occurring by chance at one in 10^(10^123) — a number that cannot be written out because there are not enough particles in the universe to write the zeros.

There are three possible explanations: necessity, chance, or design.

Necessity would require showing the constants could not have been otherwise. Nothing in physics suggests this.

Chance is where the multiverse comes in — postulate enough universes and one will be habitable. It is a serious proposal, but note what it costs: an unobservable, in principle unverifiable infinity of universes, invoked specifically to avoid a designer. That is a metaphysical commitment, not an empirical finding.

Design is the remaining option, and it is not a gap argument. We are not saying "we cannot explain it, therefore God." We are saying this is precisely the pattern that in every other context we recognise as intention.

The moral argument

This is the one that most often works in an actual conversation, because it engages how the person already lives.

Premise 1: If God does not exist, objective moral values and duties do not exist.

Some atheists accept this frankly. Richard Dawkins wrote that a universe of blind physical forces has "no design, no purpose, no evil and no good, nothing but blind pitiless indifference."

Premise 2: Objective moral values and duties do exist.

Almost nobody genuinely denies this when it matters. Torturing a child for entertainment is not merely socially disfavoured; it is wrong, and it was wrong in societies that permitted it. If morality were only cultural preference, then the reformers who opposed slavery were not right — they were merely unfashionable, and there would be nothing to say to the culture they opposed except that you dislike it.

Conclusion: Therefore God exists.

Lewis reached this from the other direction. His argument against God had been the world's cruelty — until he noticed that the objection required a standard of justice, and asked where an atheist gets one:

My argument against God was that the universe seemed so cruel and unjust. But how had I got this idea of just and unjust? A man does not call a line crooked unless he has some idea of a straight line.— C. S. Lewis, Mere Christianity

The argument from reason

Less common and quietly devastating.

If naturalism is true, your brain is the product of processes selected for survival, not for truth. Beliefs were retained because they were useful. But survival value and truth value are different things — a false belief that produces cautious behaviour survives perfectly well.

This includes the belief that naturalism is true. So the position undercuts the reliability of the reasoning that produced it.

Darwin himself felt the force of this: "the horrid doubt always arises whether the convictions of man's mind, which has been developed from the mind of the lower animals, are of any value or at all trustworthy."

Theism has no such problem. If a rational God made us to know, our faculties are aimed at truth by design.

Handling the common moves

"You cannot prove God exists." Correct, if "prove" means mathematical demonstration. Almost nothing outside logic and mathematics can be proved in that sense — not that other minds exist, not that the past is real, not any scientific theory. The standard everywhere else is inference to the best explanation, and that is the standard being applied here.

"Religion has caused most of the wars." Historically shaky — the Encyclopedia of Wars classifies a small minority of recorded conflicts as primarily religious — and the twentieth century's atheist regimes killed on a scale no religious war approached. But do not lean on the body count. The better answer: the question of whether Christianity is true is separate from whether Christians have behaved well. Both matter; only one determines whether Jesus rose.

"I only believe what I can see." Then you disbelieve a great deal you rely on: other minds, the laws of logic, mathematical truths, the past, moral facts, and the reliability of your own memory. None is empirically observable.

"Faith is believing without evidence." Not the biblical meaning. Pistis is trust based on grounds. Hebrews 11:1 speaks of assurance and conviction, and Jesus repeatedly appealed to evidence: "believe on account of the works themselves" (John 14:11). Thomas was given the evidence he asked for and not rebuked for wanting it.

How to do this well

Ask before asserting. "What convinced you?" and "what would change your mind?" — and be prepared to answer the second yourself. If nothing could change your mind, you are not reasoning either.

Listen for the story. A significant proportion of committed atheists have a history: a rigid upbringing, a church that failed them, a prayer that went unanswered, a death. The stated argument is often the acceptable public form of something else. If you answer only the argument, you have missed the person.

Concede what should be conceded. There are hard questions. Suffering is genuinely hard. The behaviour of Christians in history is genuinely indefensible in places. Conceding real ground makes everything else you say more credible.

Know the limits of what you are doing. Arguments remove obstacles. They do not create faith. Paul reasoned in the synagogue and in the marketplace, and he also wrote that "the natural person does not accept the things of the Spirit of God" (1 Corinthians 2:14). Both are true, and holding both keeps you from despair and from arrogance.

Paul's model at Athens is the one to copy (Acts 17:22-31): he began with what they had built, quoted their own poets, engaged their categories — and then went to the resurrection. Some sneered, some wanted to hear again, and some believed.

That is a normal set of outcomes. Expect it.