Isn’t it more plausible to suppose that all that exists is matter, since such an account posits only a single kind of substance whereas theistic accounts must posit something else in addition to matter? Ever heard of Ockham’s Razor?

Simplicity is a genuine virtue in theory choice, so the objection is not silly. But counting substances is the crudest possible way to apply it, and by the measures philosophers actually use, the ledger is not obviously in naturalism's favor.

1. The razor is not made of matter. Ockham's razor is a methodological principle — a rule governing inference — and as such it is abstract, not a lump of anything. The person wielding it is already committed to a non-physical thing: a norm that tells us which theories to prefer. That does not prove God, but it does show the “only matter exists” toolbox is incomplete.

2. There are two kinds of simplicity. Philosophers distinguish ontological parsimony (few entities) from explanatory parsimony (few unexplained stopping points). A theory can be lean in nouns and extravagant in brute facts. The razor delivers no verdict until you say which kind you mean, and the objection silently switches between them.

3. Naturalism has a long inventory too. Matter, laws of nature, the values of physical constants, initial conditions, conscious experience, mathematical truths, moral facts, and the reliability of human reason. “One substance” is a rhetorical summary, not a count. Say “matter and its properties” and you have not reduced anything; you have renamed the list.

4. Classical theism posits one ultimate reality. God is not an item beside the universe, added to it like a second substance in a warehouse. He is the ground of everything: in him “we live and move and have our being” (Acts 17:28), and all things hold together in him (Colossians 1:16-17). Classical theism holds that God is absolutely simple — no parts, no composition. “Matter plus God” is a strawman, not the doctrine.

5. Matter does not explain matter. Every physical thing we meet is contingent: it might not have existed, and it might have been otherwise. A brute cosmos is a stopping point, and unexplained stopping points are precisely what explanatory parsimony counts. Hebrews treats this as a matter of understanding rather than assumption: “By faith we understand that the universe was created by the word of God” (Hebrews 11:3).

6. Consciousness is a different kind of fact. Adding neurons describes the correlate of experience, not the experience. Why is there something it is like to be you, rather than information processing in the dark? The “hard problem” is named by a naturalist, David Chalmers, precisely because more matter does not solve it by addition.

7. Reason needs a ground to be trusted. If beliefs are selected for survival rather than truth, the confidence that our cognition tracks reality is a happy accident. Plantinga's evolutionary argument against naturalism presses this; it is contested, but it is not dismissible, and it turns the razor back on the materialist's own faculty of reason.

8. The world is rationally transparent. The universe is described by mathematics of startling elegance, and it did not have to be. “The heavens declare the glory of God” (Psalm 19:1), and Paul says his invisible attributes “have been clearly perceived... in the things that have been made” (Romans 1:20) — claims about intelligibility, not just beauty. A mind behind the cosmos accounts for a readable world more cheaply than blind matter that happens to be legible.

9. The razor is a tie-breaker, not an argument. It applies only when two theories fit the data equally well. It cannot establish that naturalism fits better; that requires evidence, and the evidence is the actual dispute. Using the razor to settle the question before the evidence is in is not parsimony, it is a shortcut.

10. Simplicity has never been the test of truth. Heliocentrism was not obviously simpler to calculate than a well-tuned system of epicycles, and it won on observation. We do not choose worldviews by counting nouns in a sentence. We choose them by which one explains the most with the least left over — and that is an argument, not a slogan.

Ockham's razor tells you to prefer fewer unnecessary posits, not fewer kinds of thing. The real question is which account leaves fewer unexplained stopping points, and that question has to be argued on the evidence.

Sources: William Lane Craig, Reasonable Faith; Edward Feser, The Last Superstition; Alvin Plantinga, Where the Conflict Really Lies; David Chalmers, The Conscious Mind.

Related challenges:
• IF God exists, He’s maniacal. If He WANTED to forgive sin, He’s 'all-powerful' and 'all-loving' – He could just, SHAZAM, forgive sin. Instead, He sends down His only Son to be slaughtered and murdered to take care of the sin problem. Now THAT’S evil!
• I hear a lot about “intelligent design.” Has this now proven God and falsified evolution?
• How would you respond to Victor Stenger’s stinging assertion that religious argument leads universally to dismal failure and untold suffering?