Oct 212014
Numbers in an abstract world

Do numbers really exist in an abstract world?

At the very foundation of modern mathematics you will find a belief in a mysterious realm that lies outside this physical world. Inside this realm all numbers from all number systems inherently exist. This abstract world has always existed and always will. And without this imagined place it is claimed we would not even be able to prove that numbers exist.

But how could this strange state of affairs have occurred? Maybe it was the desire to prove that numbers ‘exist’ rather than can be constructed that led down this extraordinary path. Should we really accept that saying numbers exist in an abstraction is somehow a valid reason to bypass the need for any physical existence?

An idea has a physical presence in our mind (via the chemistry of the brain) or where it is documented (e.g. via the ink it is written in). In this respect, abstract ideas need a physical manifestation in order to exist. Ideas might include numbers, the rules of how to create more numbers, or even the rules of a how objects behave in an abstract system.

If I imagine some cats controlling a spacecraft and landing on Mars then this idea can be said to exist in my mind. But I cannot conclude that space cats must exist on Mars simply because I can imagine it. Instead of Mars I could use an imaginary planet and call it an abstract thought, but this still does not prove that space cats or the imaginary planet actually exist themselves. Similarly, being able to think about numbers does not prove that numbers themselves exist in an abstract world. To say something can exist without any physical presence at all is a belief in the supernatural, and this is exactly what mainstream mathematics is based upon!

If I write down a big number that has never been written before, I have simply constructed it for my own use. I have not brought it into existence for everyone else to use, and I have not fetched it out of a mysterious realm containing all numbers. But mainstream mathematicians disagree. Rather than talk in terms of construction, they prefer to talk about existence as they insist all numbers already exist.

This belief (called mathematical platonism) is that with absolutely no physical manifestation at all, an infinite number of numbers (or possibly many infinities) just ‘exist’ in an abstract realm that has existed since the start of time.

Now let’s see how this concept is used. Consider this simple fundamental proof…

Given any two different real numbers a0 and b we can construct another real number halfway between them. If we call this new number a1 then we can show how a new number (a2) can be created halfway between a0 and a1.

This is claimed to inductively show there are an infinite number of reals between a0 and b.

To me, this is just two statements of fact that prove we can construct more numbers endlessly. But most mathematicians see this as two statements of fact that apply to all the numbers between a0 and b. And since all the numbers already ‘exist’ (in an eternal abstraction), then it must apply to an infinite number of numbers.

Importantly, endless and infinite are not the same thing. Infinite implies you can have an infinite number of something whereas endless implies an open-ended process where you can never reach an end point, and so you can never have an infinite number of anything.

The word ‘abstract’ has been used to supposedly justify numbers can inherently exist in a realm outside of reality. And once this strange idea has been accepted, the notion that infinity must also exist is a very small step indeed.

Mathematics would be a more staid and boring subject without all the weird and wondrous things that infinity brings with it. But do we really want mystic beliefs at the heart of a discipline that is traditionally associated with logic and rigour?


  2 Responses to “Mainstream mathematics is based on a belief in the supernatural”

  1. Hi

    Great post. I sympathize with you fully. But how is one to stop a religion – the fetishism of ZFC – when it is in full swing?

    I suspect it will burn itself out eventually as it is pretty much unproductive and sterile. When ever infinity pops up in physics, they try very hard to get rid of it – Feynman and renormalization and all that, which all links back to scaling relationships.

    I like the idea of just replacing the word “infinity” with “endless”. Its very subtle. Doesn’t change any of the math per se, just how people think of it.

    Now, I don’t think something has to be physical to be “real”. So, I am not bothered by the Platonic idea. Let’s say you grant this idea for the sake of argument. Just because we accept that things can be nonphysical doesn’t imply they are infinite. Nonphysical things are expected to be finite and potentially endless, just like physical things. The cat on Mars does indeed exist in imagination, and, in that sense, certainly exists.

    Now, there is only one place where the idea retains any semblance of legitimacy, and that is in its association with the concepts of “being”, “existence” and “consciousness”. I think Nicolas of Cusa conceptualized the issue correctly. He called it the “Maximum”, and equated it both with One and with being. It is not endless. It is “fullness” or “completeness”. There can only be on instance of it.

    Just some random thoughts. Again, thanks for the great post and wonderful web site.

    Best wishes,


    • Thank you for the positive feedback.
      Using words like ‘endless’ would be a good start. However, many more changes would be required to remove the notion of infinity from mathematics.
      I am planning to do some more posts to address some of the more obvious of these changes. For example, I’d like to talk about the mathematics of endless sequences; particularly the Riemann Zeta function at -1 and the question of does 0.999… equate to 1.
      Regarding the imagination, I would say that the ‘idea’ of a cat on Mars can exist in the chemistry of the brain, but saying the idea exists is different to saying ‘the cat on Mars’ exists in the imagination. For example, it is not possible for every aspect of the whole planet of Mars to exist in a human brain. Some people even argue that infinity must exist because they claim they can imagine it.

Sorry, the comment form is closed at this time.