Fantastic, this provides another teachable moment for you! π
My comment presented something called a hypothetical situation. It is an example of how particular circumstances can lead to a specific outcome. The key takeaway is that--and I recognize this can be confusing!--it does not make any claims outside the details contained within the hypothetical.
This answers both of your questions, but let me make it easy for you: I don't, and because I made these circumstances be true in this hypothetical situation.
If your brain creates the illusion of a unicorn, then the presence of the illusion is real, even if the unicorn is not.