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Philosophical Arguments About God’s Existence17 min read

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arguingaboutgodsOne of my favorite atheist philosophers is Graham Oppy, Professor of Philosophy and Associate Dean of Research at Monash University and Associate Editor of the Australasian Journal of Philosophy. Having read (and reread) the opening to his awesome book, Arguing About Gods, I wanted to summarize his list of philosophical arguments that pertain to the existence or non-existence of a monotheistic God.

Why? Because it helps me organize these ideas, and because, well, if you have to ask…

Major Arguments


1. Ontological

While ontological arguments themselves are some of the toughest to understand, the definition of them is not. Oppy writes:

Ontological arguments start from definitions, or claims about the contents of conceptions or ideas, or claims about what is conceivably or logically possible and – without the addition of further premises that are not claimed to be knowable a priori – draw conclusions about the existence or non-existence of monotheistic gods. (p. 2)

In other words, no data, just presuppositions. Once you start including data you’re into cosmological arguments.

Many readers may be familiar with Anselm’s ontological argument for God, which may be summarized this way:

If a necessarily-existing God is possible, He must exist in all possible worlds.

Of course, WHY this is true is argued in many different ways across history, from  Anselm and Rene Descartes through Leibniz, Sadra, Godel, to modern philosophers such as Alvin Plantinga and William Craig. 1

Oppy notes that such arguments can also be parodied to try to prove the opposite, such as in the Evil God Argument, as argued by atheist Stephen Law (though I argue that this argument is not analogous and fails because an evil God would not fulfill the attribute of greatness). 2 3

Oppy also argues that general mereology (the study of how parts of the whole interact) is a priori (definitional), and could be considered ontological, but again, when you start using observations in your mereology, you are now into cosmological arguments.

2. Cosmological

Again, Oppy provides a great definition, though it broadens the scope of such arguments beyond the simple first-cause argument. This broadening subsumes the Moral Argument, which is often listed separately from the Cosmological Argument.

Cosmological arguments for and against the existence of monotheistic gods are arguments with key premises that advert to very general structural features of the universe and/or our ways of theorizing about the universe – temporal structure, modal structure, causal structure, explanatory structure, intelligible structure, axiological structure, and the like – of which it is not plausible to claim that we have an exhaustive a priori knowledge.

To unpack this, we can argue for the existence of God (or against)4 using the following variations of cosmological (structure of the universe) arguments:

  • Temporal Structure: The A and B theories of time 5 are one important type of time argument. Are we existing and growing in one moment of time (A), or are the past/present/future all existing at once (B), so that we could travel back in time? If B is true, subsequent logic may require an infinite past, or deny a start to space/time. And if there is an infinite past, that may mean we don’t need a creator who started time and space. But if science has proven that time and space did have a beginning (Big Bang), does that mean that the A-theory of time is true, and therefore, we need a prime mover, a Creator?
  • Modal Structure: Modal data are facts about how things could, must, or could not have been. They involve the impossibility of some counterfactuals – is God impossible? Is atheism impossible? When we compare reality to what it implies we see this type of logic (e.g. if the universe has a beginning, does that mean God must exist? – yes, these categories overlap a little). For modal arguments, think only in terms of possibilities (only must or cannot, yes or no), not probabilities (could).
  • Causal Structure: This is the meat and potatoes of the Cosmological argument. Nothing comes into being uncaused, but has a cause before it. If the Universe and time had a beginning, they needed a prime mover. And that prime mover had to be outside of time and space, incredibly powerful, and volitional (it had to choose to change what had existed). That sounds like any common definition of an almighty God.
  • Intelligible Structure: This is a very interesting argument, and goes something like this: if the universe is intelligible and bound by laws that make for consistency and logic, such a world must have been created by a like being – one of logic. In addition, it may be argued that such a design was made so that we creatures COULD know the truth about God and reality. Analytic philosopher and intelligent design proponent Jay Richards has even argued that the unlikelihood of having a moon that provides a nearly perfect solar eclipse shows that God wanted us to understand the universe (no other known planet has a moon that is precisely spaced between it and the sun as to create a perfect eclipse).6
  • Axiological Structure: Also known as the Moral Argument for God, the existence of moral absolutes is posed as an argument for an independent law giver.

I’m not sure yet what Oppy would say, but I would put the Euthyphro Dilemma in this last category of axiological arguments against God. This argument is commonly stated:

“Is what is morally good commanded by God because it is morally good, or is it morally good because it is commanded by God?”7

This argument is asserting that God is not necessary for good to exist since good exists separate from God. Either that, or good is only so because God commands it, and then good is arbitrary (it’s not intrinsically good or bad). Of course, William Craig has well argued that this is a false dilemma – God declares what is good because He IS good, not because goodness exists apart from him or is only so because of an authoritative declaration (a.k.a. Divine Command Theory).

3. Teleological

Commonly known as the argument from design (telio meaning with a specific end (telios) in mind), Oppy likes to define it this way:

Arguments with key premises that appeal to particular (contingent) features of the world thare alleged to be prima facie plausible instances of intelligent design. (p. 3)

He has to get those Latin phrases in there, eh?  While I prefer a simple subgrouping of these arguments into macro (fine tuning of the universe) and micro (informational content of DNA), Oppy goes for a fuller definition of the types of teleological arguments, but does admit that the two I’ve mentioned are often considered the strongest, but others may be equally good:

While it may be plausible to claim that the strongest teleological arguments are those that appeal to certain cosmogonic and biological features of the universe, it is not clear why this consideration should lead us to suppose that arguments from consciousness, or the existence of language, or the existence o politically structured societies, and the like, should not also be classified as teleological arguments. (p4)

  • Cosmogonic: Studies of the origin of the universe, including the position of our Earth in a habitable zone, and many conditions conducive to life, and as queried above in the Cosmological argument, “Is there a design conducive to human discovery?”
  • Physical: How is it that the physical constants such as nuclear and gravitational forces are so finely tuned, that if they were changed even slightly, no universe would exist?
  • Chemical: I’m not sure of any chemical arguments, but the amazing properties of water and carbon and their role in life might be important arguments for design. However, you could argue for godless evolution with chemical biogenesis as the creator of living things, though this has yet to be proven in the laboratory.
  • Biological: Why does DNA seem to have informational content? Does information require and intelligent source, or can it evolve from disorder, and if so, by what observable or testable laws? And how can we explain the origins of life with or without God? The mere complexity of living systems seems to fly in the face of natural causes for such phenomenal designs. Even atheists can’t help using the term “design” when referring to nature, even though they know they shouldn’t. Oppositely, you could also argue that Darwinism has removed God or an intelligent creator as a necessary cause for complex life.
  • Psychological: How can consciousness and mind be explained? As merely an emergent property of physicalism, or as a reflection of a mind that created it, or as a separate independent entity (spirit)?
  • Social: Why do creatures and men organize themselves into societies? Does this indicate a God who programmed them to migrate or organize?

Other “Minor” Arguments

Other classes that Oppy lists are as follows.

4. Other Moral Arguments

Although the standard moral argument for God (moral absolutes exist, therefore God exists) is now, according to Oppy, part of the Cosmological Argument, there are other moral arguments for and against God that are moral, but that may be put into other categories.

For instance, he argues that the following probably belong in the Teliological argument:

  • Distribution of goods and rights in societies: This argument is actually an important one – if God is just and good, why are so many born into terrible situations not of their own making, and why do so many die without hearing the gospel? (I have tried to approach this topic in Divine Hiddenness and Demographic Distribution)
  • Existence of conscience and intuition: If societies across time and location come to a consensus on at least some moral absolutes, or if most of us experience both conscience and intuition, what does this say about our nature, and God’s? (I have discussed the Biblical view of conscience and intuition elsewhere).8 9

I would argue that the problem of the Hiddenness of God would fit here as well.

Additionally, the following moral arguments may be classified as minor evidential arguments

  • Mismatches between happiness and deserts: Why are some people poor but happy, while others are rich and unhappy?
  • Alleged greater happiness of believers: If believers are more successful in life by various measures such as marriage retention or happiness, does that indicate that their beliefs are true?

5. Arguments From Evil

This important argument cuts both ways. There are good arguments for the non-existence of god, (how could a good God allow evil to exist), for which there are many responses, known as theodicies. None of these responses argue that the existence of evil proves there IS a God, they merely attempt to argue that the existence of evil does not make a good God logically impossible, or even improbable.

It is widely held in philosophy that Alvin Plantinga’s free will defense has defeated the argument that the existence of evil demands that an omni-benevolent and omnipotent God cannot exist. He shows that it is at least logically possible that a good God could have reasons for allowing evil.

Oppy argues that these arguments can be classified as both teleological and moral arguments, fitting into two of our major categories above.

6. Non-evidential Arguments

Oppy proposes another grouping which again may span some of the primary categories. This catch-all, in his mind, includes:

  • Pascal’s wager: A smart person would, based on the mere consequences of being wrong, bet that God exists. Read my four part series on this here.
  • James’ arguments on behalf of the will to believe: Philosopher William James discussed why it might be reasonable to believe something without prior evidence, and why faith in God may work this way. 10 11
  • Kant’s prudential moral argument: Philosopher Emmanuel Kant argued that the goal of humanity is to achieve perfect happiness and virtue (the summum bonum) and believed that an afterlife must exist in order for this to be possible, and that God must exist to provide this.12

7. Cumulative Arguments

This last grouping of Oppy’s seems to be his least favorite, but he gives some meaningful guidelines to help us to determine what are legitimate and illegitimate attempts at cumulative arguments:

There are also cumulative arguments that somehow combine these arguments into more powerful meta-arguments (or cases) for and against the existence of monotheistic gods. While this is doubtless so, there are pitfalls that we must be careful to avoid.

If we have two valid arguments, each of which entails the conclusions that a particular monotheistic god exists, then we can form a disjunctive argument that also entails the same conclusion. More generally, if we have a large collection of valid arguments, each of which entails the conclusion that a particular monotheistic god exists, then we can form a multiply disjunctive argument that also entails that same conclusion.

However, it should not be supposed that a ‘cumulative’ argument that is formed in this way is guaranteed to be a better argument than the individual arguments with which we began (even if we are properly entitled to the claim that the arguments with which we are working are all valid). For on the one hand, if all of the arguments are defective on grounds other than those of validity – for example, because they have false premises, or because they are question-begging – then the cumulative arguments will also be defective.

But on the other hand, if even one of the arguments with which we began is not defective on any other grounds, the it is a cogent argument for its conclusion, and the cumulative argument is plainly worse (since longer and more convoluted).

So at the very least, we have good reason to be suspicious of talk about a cumulative case for the claim that given monotheistic god does – or does not – exist that is based upon a collection of (allegedly) valid arguments for the claim….

But – despite the appearance of occasional claims to the contrary – it should not be supposed that separate (valid) arguments for or against the existence of a given monotheistic god ever stand in this kind of relationship to one another. The premises in a valid argument may well stand in need of further support before it is plausible to claim that one has a cogent [cumulative ] argument…

Talk about a cumulative case makes much more sense if we suppose that we are dealing with ‘probabilistic’ – or ‘inductive’, or ‘evidential’ – arguments….

Summary of Cumulative Arguments

OK, so you skipped that big quote, huh? Here’s what he says in a nutshell about cumulative arguments:

  • In general, we should be suspicious of supposed cumulative arguments
  • Many valid arguments put together do not mean you have a cumulative case – you must also argue why these logically stack
  • Individually valid arguments may not be stackable because they may entail different or contrary premises, or be begging upon one another (you assume one to prove another).
  • Such arguments may be more proper when dealing with probabilities, induction from the facts, or evidential approaches

godscrimesceneInterestingly, noted apologist and cold case detective J. Warner Wallace approaches his justification of God’s existence using all three of these types of cumulative approaches (probabilistic, inductive, and evidential) in such books as God’s Crime Scene: A Cold-Case Detective Examines the Evidence for a Divinely Created Universe and Cold-Case Christianity: A Homicide Detective Investigates the Claims of the Gospels.

Wallace is a thoughtful and mellow dude, but very organized and smart when it comes to evidential argumentation, you can check out his podcast.


Graham Oppy is one of the reasoned contemporary atheist thinkers, not one of the loudmouthed antagonists. For those wanting to think philosophically about God, his writings are gems. And hopefully, this introduction to his organization of philosophical ideas about God has been as enjoyable to you as it has been for me.

BONUS: Graham Oppy interview on Conversations From the Pale Blue Dot

  1. Ontological argument (wikipedia)[]
  2. The Evil God Challenge – Flipping Arguments ([]
  3. Why the Evil God Challenge Fails ([]
  4. Modal Arguments from Atheism ([]
  5. A and B Theory of Time and the Kalam Cosmological Argument (William Lane Craig) (youtube)[]
  6. The Privileged Planet (youtube)[]
  7. Euthyphro Dilemma (wikipedia)[]
  8. The Tripartite Man 2: Spirit – Intuition ([]
  9. The Tripartite Man 3: Spirit – Conscience ([]
  10. The Will to Believe (wikipedia)[]
  11. Are you a Christian because of your experiences, or because of logic? ([]
  12. Argument from Morality (wikipedia)[]