God, Santa, and The Tooth Fairy

[Mister Agenda]

[...] by 'exist' I mean occupy space in people's minds. They never actually exist in a material sense.  

Do minds have space in them? I'm thinking that mind, though associated with the brain, is not itself something which has extension. Certainly a given form in someone's mind doesn't seem to have a measurable space that it occupies. (I'm guessing you're using this as a metaphor.)

If they exist in the mind, then they do exist in a particular way. 

If they exist in the mind but not in a material sense, then there are things which can exist non-materially.

How would you define this non-material realm? Can the things which "occupy space" in people's minds be in some way real, like numbers? In terms of hylomorphism, we can talk about things of which the forms exist (morphe) without the matter (hyle). This would certainly be in line with standard theology.

There are no numbers without a brain, computer, abacus, piece of paper, or the like to be imprinted on or processed within. All of those things take up space. Numbers and ideas and concepts can't be demonstrated to exist without matter and energy in space and time.