Occam's razor, or the law of parsimony, states that the simplest explanation for any given data is most likely the correct one.

Some have attempted to use Occam's razor in a metaphysical sense, to say that, for example, God is unlikely because to assume that God exists introduces additional, and unlikely, complexity. However, I'm wondering how this can be applied. The Wikipedia article for Occam's razor gives a few justifications, but the only justifications that seem to work for metaphysics are the mathematical ones (correct me if I'm wrong), for all the others are either empirical, which is not related to metaphysics, or "aesthetic," which does not seem to be very rigorous.

The mathematical justification seems to state that because the probability of the assumptions needed, for example, to say God exists is less than 100%, each additional assumption decreases the probability of God. However, I have a few questions about this.

  1. Why assume that the probability of any two given metaphysical ideas are the same? For example, how can you assign any probability to whether or not God exists? Why assume a uniform distribution any more than any other distribution?

  2. Why assume that the assumptions to be made have a non-100% probability? Of course, you could then say that they are not really assumptions, but how could you justify that they really are assumptions at all?

  3. Why is there a distinction between "positively defined" and "negatively defined" assumptions? For example, to say that God does not exist, you would have to assume that there is no being that exists that is all-powerful, no being that exists that is all-knowing, etc. It seems fairly easy to come up with additional assumptions that have to be made even in a "negatively defined" case, and how can you meaningfully assign probabilities to these assumptions?

I've also seen justifications based on minimum description length and Kolmogorov complexity, but I don't see how these computationally-based ideas have anything to do with metaphysics. How can one say that a metaphysical reality is in any way defined in a computational sense? Do simple statements that can be said to define metaphysical realities, such as x is true, y exists, etc., somehow link to computation?

While I don't really see any problems to these objections, I assume that there is at least some validity in using Occam's razor in a metaphysical way, given that so many well-known (and lesser-well known) atheists, such as Richard Dawkins, base their beliefs off of it. So what, if anything, is wrong with my objections?

  • 1
    Empirical is not unrelated to metaphysics, it is a basis of it, although not the only basis if one is not an empiricist. What we are looking for is a plausible and parsimonious explanation of the totality of our experience, empirical and otherwise, if any. If we can find an equally plausible, but more parsimonious, metaphysical picture without God then we are justified in dropping him from the picture. it is a pragmatic justification, not a metaphysical one.
    – Conifold
    Jun 19 '19 at 22:49
  • "the simplest explanation for any given data is most likely the correct one." So wouldn't that mean Occam's Razor can't be used metaphysically? ... there's no data by definition. What would be an example of a mathematical justification for something metaphysical? With regard to god I need to know, and is not defined above, what 'exists' means? How does something exist in supernatural domain since supernatural (metaphysical) means unmeasurable? Does the statement 'god is metaphysical' or 'god does not participate in the natural world' mean that god does not exist? Jun 20 '19 at 4:41
  • Occams' Razor is used all the time in metaphysics. It tells us nothing about whether there is a God but it does lead us to believe there are not two of them. The suggest that the correct 'explanation of everything' will be the most parsimonious. As metaphysics is all about reductution it is bound to be a search for the most parsimonious theory, Thus, for instance, we can reject Democtritus' 'atoms and void; model for having way too too many theoretical entities. .
    – user20253
    Jun 28 '19 at 15:37
  • I don't think there is anything wrong with your mathematical observations but as I suggest in my answer the Razor has metaphysical applications to the problem of universals, a problem neither mathematical nor necessarily involving God and not specially tied to aesthetics even if as some suppose there are aesthetic universals. 'The' problem of universals ? There are many but it's clear with which problem Ockham was primarily concerned. Best - GLT
    – Geoffrey Thomas
    Dec 20 '19 at 13:47
  • I feel the question here is confused. There is a general question about Occam's Razor and a specific question about God. The latter is easy since the Razor tells us nothing about God, while the former is more interesting.
    – user20253
    Dec 20 '19 at 14:10

Let me point out, first, that Occam's Razor is not a law; it's a rule-of-thumb that has more to do with pragmatics and aesthetics than necessity. It's a good rule of thumb, sure, but it is based on an a priori belief that the universe as a whole conforms to what human minds count as parsimony.

That being said, the main issue with applying Occam's Razor to metaphysics (or to anything, really) is that the concept of parsimony is sensitive to context. Parsimony is a conservation issue — by which I mean it tries to create a constant, minimal, necessary and sufficient ground for a field of knowledge — and so we need to consider what qualities we are trying to conserve before we can apply it fruitfully. In the atheist/theist divide pointed at above, atheists generally focus on the material/physical universe to the exclusion of everything else, and within that context it may very well be more parsimonious to assume there is no God. Theists, by contrast, are not overly concerned about the physical world. They focus on the social/moral world — the world of human experience and behavior — and within that context it may very well be more parsimonious to assume there is a God. God may be an unnecessary explanation for the Big Bang, but are Newton's Laws useful and relevant to an understanding of ethics?

The conflict between these groups is seemingly endless because both sides refuse to engage the context of the other: theists dismiss valid statements of science, while atheists reject theological moral, philosophical, and experiential arguments out of hand. There will not be a resolution to the issue until all those involved are willing to engage a larger context, and we cannot really talk about parsimony until that occurs.

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    A sensible answer. Reminds of another comment by @CriglCragl that «Western thought is still stuck in the idea religious claims are epistemological» Jul 29 '19 at 16:31
  • Good answer, but I want to nitpick: "Theists, by contrast..." should necessarily assume that there is a god instead of "may very well", by definition of their own 'theist' quality.
    – user31740
    Aug 19 '19 at 13:16
  • @William - well, yes, you're right as a matter of definition, but I was talking about the parsimony of the reasoning. Think of it this way... If there was a person with no opinion who was trying to decide whether God existed, then context matters. if s'he is focused on the material/physical world then the idea of God might seem extraneous; if s'he is focused on the social/moral world then the concept of God might seem elemental. S'he would come to beliefs accordingly. Aug 19 '19 at 14:36
  • @TedWrigley - I would agree with your point. But a person focused on the material world still has to explain what it is and where it came from, so I'm not sure this is a good example.
    – user20253
    Dec 20 '19 at 14:13
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    @TedWrigley - There are plenty of theories that don't work. I see no use for them.
    – user20253
    Dec 21 '19 at 12:41

I'm not sure this is exactly what you're asking, but it's very much possible to use Occam's razor with religion.

Of these two hypothesis:

  • Humans made a mix of the beliefs and legends of their time about the world and its origin, based on their current knowledge, it stuck orally, and eventually got written in a book that was then described as the original word of God.

  • God spoke to humans, and purposely gave an incomplete and incorrect depiction of the world (no mention of viruses or bacteria, plants created before the sun and moon[1]), and gave incoherent or plain arbitrary recommendations ("never cook a young goat in the milk of its own mother" [2]) instead of recommendations that could be actually useful ("wash your hands regularly and keep you waste far from your house").

which one seems more simple? And if you try to find reasons for God to give factually wrong information in the Bible, that would make your hypothesis even more complex and Occam razor would favor the first one even more.

This doesn't prove God doesn't exist of course, but here Occam's razor can be used for question related to religion (is the Bible man-made or the true word of God?) that can be used for a reasoning about the existence or God.

Though it's not a metaphysical question, and IMO I don't think Occam's razor can be used for something purely metaphysical in the sense that we have no data on any of the hypotheses we want to test.

[1] : Genesis somewhere

[2] : Exodus 23:19

  • Besides the Bible references would you have references to others taking a similar view about Occam's razor? These would support your answer and give the reader a place to go for more information. Welcome! Jun 28 '19 at 16:31
  • @FrankHubeny My source video is in French, but it has English captions. Here's the link. Occam's Razor is not directly mentioned but he uses Bayesian inference reasoning and it's closely related to Occam's Razor Jul 1 '19 at 19:19

The same Occam who has a razor named after him also said:

Only faith gives us access to theological truths. The ways of God are not open to reason, for God has freely chosen to create a world and establish a way of salvation within it apart from any necessary laws that human logic or rationality can uncover.


He believed that science was a matter of discovery and saw God as the only ontological necessity.

from Wikipedia

Emphases added in original showing Occam using his razor in the context of his calling...


  1. Occam was a theologian
  2. Occam's razor is named after said theologian

People wanting to affirm the second and ignore the first are suffering from acute tunnel-vision or mendacity.

Thought experiment

Here's a list of musicians who objected to Trump using their music.

If William of Occam – the theologian – were alive and found all the great anti-theists using his name to justify their godlessness would he say "It's ok! " or would he issue "cease&desist" orders?

Hint: Check what tough letters he sent the pope for not following the injunctions to poverty in holy-scripture.

  • I am downvoting the answer because it doesn't directly adress the question and ends with an unrelated afirmation, besides the bad formatting.
    – user31740
    Jul 28 '19 at 17:39
  • Be my guest 😀😆😈. Yet I appreciate the comment @william. (most down voters hide under anonymous cowardice) Jul 28 '19 at 17:46
  • @william added emphasis to show the connection with the question. IOW to show how the theologian William of Ockham used his razor as a justification of his faith Jul 28 '19 at 17:51

An interesting point about your question is that Occam first applied the Razor - though the term is not his - to a metaphysical issue, the problem of universals.

Ockham was a nominalist - he denied the existence of "universals." What are they? Let us begin with what they are not. Universals contast with particulars. Particulars are the individual things that populate the universe - you, the hive of the bees in the park, the Eiffel Tower, Planet Earth. Universals are supposed to be the properties that multiple individual things have in common. For example, Socrates and Plato are particulars, and both philosophize. Does that mean that the statement "Socrates and Plato both philosophize" describes three things - the two men plus the universal to which the two individuals belong? Ockham's answer is no. According to Ockham, the two individuals exist and there is Socrztes's philosophizing and Plato's as well. Each of these properties is unique to the individual who has it. There is no universal here - there exists no property of philosophizing that is shared among the particulars. It is the human mind's invention of concepts (in this instance, the concept of philosophizing) that fosters the illusion that universals exist. (Elliott Sober, Ockham's Razors, ISBN 10: 1107692539 / ISBN 13: 9781107692534. Published by Cambridge University Press 2015-07-23, Cambridge, 2015: 9-10.)

This shows how the Razor can be used metaphysically whether considers it a correct use or not. Sober further refers to Ockham's use of the Razor in connexion with the problem of change, of explaining what happens when change occurs. I take change to be in broad terms another metaphysical issue, not least because universals can be invoked in handling it.

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