> We're talking about a practice whose goal is to manipulate the brain, an organ that has been called the most complex object in the universe, something that centuries of science have only begin to understand, and that comes with vast and poorly understood diversity across people.

You seem to be comparing meditation to neurosurgery. I have no idea why you think this comparison is valid. Meditation is voluntary control of attention, which you've been doing all of your life, not neurosurgery. No doubt using this in novel ways will present challenges.

> To claim that a certain group of monks has figured out a foolproof and risk-free formula for exploring altered states of consciousness seems implausible.

Why? Democracy was invented thousands of years ago, and we've been through many other systems of govenment since, and yet now everyone believes that democracy is the best way to organize a highly complex global system of intelligent agents. Does it seem implausible to you that a system of governance that's thousands of years old is still the best we know?

Frankly, I have no doubt that a tradition that's thousands of years old and that has had hundreds of thousands of adherents in that time, could have worked out most or all of the challenges it raises. That's a huge sample set if you were analyzing this scientifically, and these spiritual practices were quite systematically explored.