Contemporary academic philosophy has some rather crazy ideas in it. David Lewis claimed that every possible parallel universe exists (
modal realism), and is just as real as this one – our universe is the "real" or "actual" one only because it is ours. Takashi Yagisawa takes that one further, and argues that possibility is simply another dimension like space and time (
extended modal realism), and that my existence includes not just who I am in this world, but extends to equally include my existence in other possible worlds, and even impossible worlds (logically contradictory universes).
Daniel Kolak claims that only one person actually exists (open individualism), and everyone is the same person, it is just that most of us haven't realised this fact yet. Graham Priest rejects the law of non-contradiction, and argues that it is possible for a proposition to be equally true and false, at exactly the same time and in exactly the same way (dialetheism), and has even suggested that these true contradictions may exist in the real physical world, not just in abstract thought about paradoxes. Nick Bostrom argues that we may be living in a computer simulation, and if we are not, that's bad news, it is evidence that humanity is doomed, or at least that our prospects as a species are not as bright as many hope (the simulation argument). David Chalmers argues that conscious awareness is a property not just of humans and (higher?) animals, but rather that everything in the universe is conscious, even inanimate objects such as rocks, stars, planets, galaxies, even cells and molecules and atoms and subatomic particles (panpsychism).
Are these ideas "irrational"? Rationality is in the eye of the beholder. But they are just as much "out there" as those of many of the great religious philosophers–whether Buddhist, Christian, Hindu, Islamic, Jewish, etc.