"If it's not possible to create an illusion of something being false, you might not need to travel to other planes to guess it would be true there.  To say that you can't make an illusion of something, doesn't narrow down what kind of future follows from the past - we can make an illusion of a plane where jumping up puts you at the bottom of an ocean, instead of off the ground.  Even if in all previous history, jumping just lifted you off the ground a bit, we can make a detailed illusion of a world where that happens the first trillion times, and on the trillion-and-first time, you end up under the ocean instead.  So if math is about propositions we can't make even an illusion deny - then why is math any good for building bridges?  We can make an illusion of a bridge falling down."

"If it's not possible to create an illusion of something being false, you might not need to travel to other planes to guess it would be true there.  But I offer the same mischievous objection as before:  To say that you can't make an illusion of something, doesn't narrow down what kind of future follows from the past - we can make an illusion of a plane where jumping up puts you at the bottom of an ocean, instead of off the ground.  Even if in all previous history, jumping just lifted you off the ground a bit, we can make a detailed illusion of a world where that happens the first trillion times, and on the trillion-and-first time, jumping teleports you under the ocean instead.  So if math is about propositions we can't make even an illusion deny - then why is math any good for building bridges?  We can make an illusion of a bridge falling down."

"If it's not possible to create an illusion of something being false, you might not need to travel to other planes to guess it would be true there.  But I offer the same mischievous objection as before:  To say that you can't make an illusion of something, doesn't narrow down what kind of future follows from the past - we can make an illusion of a plane where jumping up puts you at the bottom of an ocean, instead of off the ground.  Even if in all previous history, jumping just lifted you off the ground a bit, we can make a detailed illusion of a world where that happens the first trillion times, and on the trillion-and-first time, jumping teleports you under the ocean instead.  So if math is about truths we can't make even an illusion deny - then why is math any good for building bridges?  We can make an illusion of a bridge falling down."