BAJ draws an intriguing analogy:
People argue against the existence of God by claiming that a belief in God is not logical. Atheists attempt to dismiss God by claiming that God exists only in the mind.
Consider that numbers exist only within the mind. But can numbers be dismissed? Without numbers – the thought ephemera that allows us to make measurements (among other things) – people can’t produce anything tangible. Belief in the existence of numbers has allowed humans to do the jobs of building things, flying to the Moon and creating new console games.
Given the importance of the acceptance of the the fiction of numbers, I wonder: does it matter if God exists only within the mind? Without God – the unassailable bastion of righteousness demanding moral behavior (among other things) – civilization would never have been established. Belief in the existence of God has inspired humans to do the jobs of creating laws, establishing rights and treating decently those who might be called useless.
I had a similar utilitarian notion about the concept of “money”, but considering the way fictional money has been used to impose servitude on so many people, I thought I’d probably be shooting myself in the foot with that particular analogy.
BAJ’s argument appears to be rather less self-damaging from that perspective, any mathmeticians here who might like to take a crack at it? I imagine Derbyshire would have something to say about it.