Christians are Jewish spiritually, page-32

''But all observers see the world through the prism of their psyche--and everything is subjective''

It doesn't follow that everything, the World itself, the Planet, the Universe, is subjective because our mental perception of it is subjective, which of course it is. The World doesn't cater to personal belief. If someone happens to believe in the reality of Allah and another person in Brahma, this doesn't mean that each believer occupies their own private Universe, that for one there is an actual Allah and for the other an actual Brahma. The actual Universe/World care not for either belief, or any belief about it.