... There's zero evidence that consciousness exists outside of the physical world. There's plenty of evidence that it does exist as something brains create. There's plenty of evidence that poking it chemically or otherwise causes changes in consciousness. In some cases, scientists have some ideas about how that might sorta happen (like the release of dopamine or serotonin). No one seems to disagree that taking, say, Xanax, does something to brain chemistry and causes e.g. less anxiety.

LSD is certainly a physical chemical that goes into physical brains. Yet all of a sudden folks want to introduce a separate magisterium and insist that despite having every appearance of acting on the brain somehow, LSD is special and really does something more. And not because of any extraordinary evidence, but because, while they were tripping, they thought up some cool neato thought like, I dunno, all people are one. A thought they can't verify at all, but makes sense while tripping. And because of that, not only is their neato thought true, but LSD itself must be something paranormal because other drugs don't let them think nonsense is true.

That's essentially all of what Leary and others come down to, despite hiding it in a lot more verbiage and nicer sounding ideas.

Just because the understanding of consciousness is rather much in its infancy doesn't give people blank checks to make shit up. LSD-fueled and valid-only-with-acid ideas on consciousness should be given as much weight as LSD-fueled pictures of Pluto.