When people talk about ontological parsimony, it is generally used to add or subtract credibility from a theory about what exists 'within' the universe or multiverse. For example, it's used to discuss the likelihood of different scientific theories being true or the existence of certain particles or the existence of supernatural beings etc.

It makes sense to me in this context that the parsimonious solution is the most likely because the more parts there are to a theory, the more failure points, and the more points that may need to explained by chance events and coincidences. To use a silly example, if you claim that atoms are held together by elves rather than just fundamental forces you have to explain how the elves function, how they came to get into the atoms, why they hold them together, etc.

However, is a parismonious theory more likely to be true when we talk about pre-existing objects, things that exist without cause?

Leaving aside the question of whether anything can exist without cause, I'm not sure why the parsimonious explanation would be the most probably here. It seems intuitively true, but I'm not sure that doesn't just come from a perception of the world we live in, where parsimony is a useful guide.

People have posited various objects existing without cause before the universe existed - for example - a singularity, a single particle, a God, pure consciousness, a multiverse, all of mathematics in physical form, etc. I'm not wanting debate how plausible each of these are but if it is really the case that the simplest of these is the most probable. It seems to me that by definition, probability weights up the likelihood of different events, or different cases caused by different evets, and events happen over time and have causes. If something has always existed without cause, I'm not sure simplicity would really make it more probable.

Any answer very much appreciated! I'm genuinely not trying to push a particular theory, I'm just confused about parismony itself.

  • IMO Ontological Parsimony (aka: Occam's razor) is not a "law" but an heuristic principle that we have to use in formulating our theories/explanation. If so, the issue with "positing various objects existing without cause" can be evaluated (following purported Laplace's dictum )"do we need that hypotheses?" Commented Sep 23, 2022 at 13:21
  • Ontological parsimony is not about what is "most probably true" (it is unclear what probability would even mean here), but about what is most rational to prefer as a theory, "entities are not to be multiplied beyond necessity", in Ockham's original formulation. Reality does not conveniently prearrange itself to be expressed in our ontological theories, we have to arrange our theories to express it. If two theories both match reality (that is the "necessity") it is more rational to prefer the more parsimonious one, other things being equal.
    – Conifold
    Commented Sep 23, 2022 at 22:07
  • 1
    Applying ontological parsimony aka Occam's razor is not that straightforward and easy as intuitively thought, and worse there's opposite principle of plenitude advocated since Plato. See a recent very related post for further ref... Commented Sep 23, 2022 at 23:14
  • Our world is unimaginably complex, while the simplest hypothesis is that everything is an illusion. These limit cases show that parsimony is not a reliable guide to reality. It is pragmatically useful but must be treated with a bucket of salt.
    – Dcleve
    Commented Sep 24, 2022 at 1:44
  • But everything IS an illusion.
    – Scott Rowe
    Commented Sep 24, 2022 at 2:26

1 Answer 1


Ontological Parsimony is a guideline. It's intended to remind people to limit the number of assumptions that have to be accepted in order to accept the explanation.

Let's take the phenomena of frost appearing on windows on cold mornings. One possible explanation is that a magical figure named Jack Frost travels about and paints the windows with frosty patters. He's magical, so he can do all the windows at once, etc. Another explanation is that the temperature differential between the outside and the inside causes water to condense on the surface of the window, and the cold air freezes the condensation, forming frost.

The Jack Frost theory is very simple. There's a magical being who likes frost. The other is somewhat more complicated, and has more pieces to it. But the temperature differential theory of frost formation is more parsimonious. It deals with things we can demonstrate. It is colder outside than inside, we know that cold water freezes, we know that water condenses, so we aren't really adding any new entities. The simpler theory adds a magical being to our reality.

  • So if our question was more like, why is it that matter is so arranged that an abundant substance, water, does this unintuitive thing of expanding when it freezes, which is a big part of why life can exist on this planet? The expanding thing seems like a prior fact that has no independent cause and which isn't amenable to parsimony?
    – Scott Rowe
    Commented Sep 24, 2022 at 2:42
  • @ScottRowe your comment doesn’t make any sense to me.
    – philosodad
    Commented Sep 24, 2022 at 18:57
  • That's ok, I was just trying to come up with something I thought was similar to what the OP was asking. But if I didn't, that's fine.
    – Scott Rowe
    Commented Sep 24, 2022 at 21:03

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .