How do we know God exists?

1. 1

   What kind of question this is

   People sometimes expect this question to work like a math problem: line up the premises, turn the crank, and the conclusion is forced.

   Almost no interesting question works that way. Whether a defendant is guilty, whether a theory in physics is right, whether a person loves you — all of these are settled by weighing evidence and comparing explanations, not by deduction.

   So the honest form of this question is comparative. Given what we find — a universe that had a beginning, physical constants that sit in a narrow band, minds that experience things, and a stubborn sense of right and wrong — which overall picture leaves the least unexplained?

   Someone can weigh all of it carefully and land the other way. That is not stupidity, and treating it as stupidity is how these conversations go bad.

2. 2

   Why is there something rather than nothing?

   The oldest argument in the file has a simple shape. Whatever begins to exist has a cause. The universe began to exist. So the universe has a cause.

   The second line used to be a purely philosophical claim. In the twentieth century, physics made it a scientific one: the expansion of space, the background radiation left over from an early hot state, and the abundances of the lightest elements all point back to a beginning.

   The honest note, and it matters: a beginning is a claim about physics, and physics can revise its claims. There are serious cosmological models — bouncing universes, eternal inflation, quantum-gravity proposals — in which our expansion is one episode rather than the start of everything. None is established, and neither is the alternative.

   So the argument is genuinely open at that point. What it does establish, if the beginning holds, is that the universe is not the kind of thing that explains itself — and that a cause outside of space and time is at least the right shape of answer.

   • “In the beginning God created the heavens and the earth.”

     Gen 1:1 — In the beginning God created the heavens and the earth.→

   • “By faith we understand that the universe was formed at God’s command, so that what is seen was not made out of what was visible.”

     Heb 11:3 — By faith we understand that the worlds have been framed by the word of God, so that what is seen hath not been made out of things which appear→

3. 3

   The dials

   Physics contains a set of numbers that the theory does not predict. They are measured, not derived, and several of them sit in narrow bands where life is possible.

   The starkest is the cosmological constant, the energy of empty space, which drives cosmic expansion. Its value is of order ten to the minus one hundred twenty-second in the natural units physicists use — that is, one followed by a hundred and twenty-two zeros beneath it. Larger, and expansion tears matter apart before a single star or galaxy forms.

   Then there is carbon, which every living thing is built from. Carbon is made inside stars through a process that depends on a very particular energy match. The strong nuclear force appears to be tuned to within about half a percent for it to work, and the strength of electromagnetism — the fine-structure constant, about 0.007297 — to within a few percent, roughly four, on the same argument.

   The astronomer Martin Rees gathered several of these into a short list of dimensionless numbers, including the ratio of gravity to electromagnetism, around ten to the thirty-sixth. His point was that a handful of numbers set the character of the whole cosmos.

   One well-known figure is deliberately absent here. Roger Penrose's estimate for the improbability of the universe's initial low-entropy state is quoted everywhere, and this site could not trace it to Penrose's own words. So it is left out rather than repeated on trust.

   What this does and does not show is the subject of the first four objections below — and they are the strongest set on the page.

   • “The heavens declare the glory of God; the skies proclaim the work of His hands.”

     Psa 19:1 — The heavens declare the glory of God; And the firmament showeth his handiwork.→

   • “Lift up your eyes on high: Who created all these? He leads forth the starry host by number; He calls each one by name. Because of His great power and mighty strength, not one of them is missing.”

     Isa 40:26 — Lift up your eyes on high, and see who hath created these, that bringeth out their host by number→

4. 4

   The one thing you cannot get behind

   Everything science studies, it studies from the outside. Brains can be measured, scanned, and mapped, and the mapping has been spectacularly successful.

   But there is one thing that is not available from the outside: what it is like to be you. The redness of red. The particular ache of a memory. Philosophers call this the hard problem, and it is called hard because the usual method does not obviously reach it — you can give a complete physical account of what a brain is doing and it seems not yet to have said why any of it is experienced.

   The argument here is modest, and overstated versions of it deserve the ridicule they get. It is not brains are mysterious, therefore God. It is that on a picture where reality is fundamentally mindless, conscious experience is a genuine puzzle — whereas on a picture where mind is fundamental, minds appearing in the world is what you would expect.

   The honest counterweight: several serious philosophers think the hard problem is a confusion rather than a discovery, and others answer it without God, by holding that experience is a basic feature of matter itself. Neither of those is a fringe position.

5. 5

   And then there is right and wrong

   The fourth reason has its own page, because Marcus Brown considers it the strongest one: if some things are genuinely wrong — not merely disliked — then goodness needs a ground that is not human opinion.

   That argument is walked in full, with the classic objection from Plato and the best modern answers, at its own door below.

   It is worth noting the shape it shares with the others. Each of these arguments points at something ordinary — a beginning, a constant, an experience, a conscience — and asks which picture of reality makes it least surprising.

   • “So they show that the work of the law is written on their hearts, their consciences also bearing witness, and their thoughts either accusing or defending them”

     Rom 2:15 — in that they show the work of the law written in their hearts, their conscience bearing witness therewith→

6. 6

   How the Bible actually argues

   Here is something people notice with surprise. Scripture never argues for God's existence the way this page does.

   It begins with a flat statement — in the beginning God — and everywhere else it points. It points at the sky. It points at rain and harvests. It points at conscience. It treats the evidence as public and already in front of everyone.

   Paul's line to Rome is the clearest case: the invisible things are perceived through the things that are made. That is an appeal to creation, not to a chain of premises.

   Which suggests the arguments on this page are doing something more limited than clearing away obstacles. They are answering the claim that belief is unreasonable. They are not the road most people actually walk to God, and Scripture does not pretend they are.

   • “For since the creation of the world God’s invisible qualities, His eternal power and divine nature, have been clearly seen, being understood from His workmanship, so that men are without excuse.”

     Rom 1:20 — For the invisible things of him since the creation of the world are clearly seen, being perceived through the things that are made, even his everlasting power and divinity→

   • “Yet He has not left Himself without testimony to His goodness: He gives you rain from heaven and fruitful seasons, filling your hearts with food and gladness.””

     Act 14:17 — And yet he left not himself without witness, in that he did good and gave you from heaven rains and fruitful seasons→

   • “When I behold Your heavens, the work of Your fingers, the moon and the stars, which You have set in place—”

     Psa 8:3 — When I consider thy heavens, the work of thy fingers, The moon and the stars, which thou hast ordained→

Each objection below is stated the way the people who hold it state it. If you hold one of these and think it is put unfairly here, that is a failure on our part — tell us.