@Poseidon,
How is it possible to conceive of something we have not observed?
Our ability to conceptualise must have some element in it which is outside of experience. In this example infinite divisibility.
If space and time where infinitely divisible, then nothing would be able to move as each movement would need to move an infinitely small amount, as Xeno's paradox shows.
Try and think along the lines of a computer animation moving across the screen. It looks like a fluid movement, but the animation moves in pixels, or quantums of space, and quantums of time. If the pixels were infinitely small, we would not be able to move as we would always be trying to move an infinitely small amount, which would always be diminishing before we could move it.
Thus :
(A) Space and time are not infinitely divisible, quantum mechanics is correct.
&
(B) For us to concieve of infinity, we could not have attained such an idea from the world, as infinity does not exist in the world (because of A).
Where do a priori concepts come from?
This is a contradiction as a priori means : 'logically and necesarily prior to'.
If we could answer the question, they would not be a priori concepts,
they would be a posteriori (acquired).
So the a priori ideas, such as math and infinity are 'not of this world'
proving that the mind is not born a 'blank slate', and thus the mind exists beyond our experience of it in this world.
We call this 'soul', rather than 'mind' in order to differentiate between
inherent knowledge (a priori or soul), and acquired knowledge (a posteriori or mind)