A reader writes:
This is why rationality is ultimately irreconcilable with faith. Scientists can now pinpoint the exact spots in your brain that light up during spiritual moments and you have found a mushroom that reproduces the effect. But instead of acknowledging this as an interesting yet completely natural sensation, you instead conclude that it’s a mushroom-shaped window into the divine. Your mind is playing tricks on you, much in the same way that your eyes play tricks on you when items move into your blind spot. (However, the effect sounds interesting; I might have to try it.)
Another elaborates on that view:
I find it fascinating how someone of faith (you) and someone who has no faith (me) can look at the exact same study and come to diametrically opposed conclusions.
Your ingestion of magic mushrooms led to a deep spiritual connection and a reaffirmation and deepening of your faith. Therefore, mushrooms are part of our connection to the divine and should not be regulated away from us. To some of us non-believers it suggests the opposite, namely that your brain is lying to you. A similar experiment showed that subjects would “feel the presence of the divine” when an electrode stimulated a specific portion of the brain. Meditation seems to trigger similar functionality by causing neurons to fire in a specific set of patterns, which have electrochemical affects on the same portions of the brain.
I don’t think you’d argue that direct electrical stimulation or a chemical message delivered to a similar spot is some sort of magic God retrieval switch. “Press here to summon God.” It seems that such a useful switch was rather oddly placed.
The brain, as an organ, likes certain types of stimulation and patterns, for the same reason that a song that you hate gets stuck in your head; “you” may not like it, but your brain certainly does. Certain kinds of messages or neuron firing patterns are highly enjoyable to the brain’s neurons – they make them feel good, at peace, interconnected. Your neurons are happy and that filters up into your consciousness to make “you” happy and connected.
If you can’t tell the difference between the presence of God and the presence of psilocybin, maybe there is no difference. No God required.
P.S. The best counter-argument I can think of is that these various techniques somehow suppress “reality’s” overwhelming input and allow you to detect the undercurrent of divinity in the Universe. The best counter-counter-argument to that is Douglas Adam’s Babel Fish: God cannot exist without faith; the Babel Fish is so obviously God’s handiwork that you don’t require faith; therefore God doesn’t exist. Q.E.D. Why create a series of unrelated obtuse methods of hooking into the divine? Why not just make it as natural as breathing?
Ask God. That’s beyond my pay grade. But more seriously, by definition, any divine manifestation in the mortal world will have some physical manifestation. Psilocybin may be a kind of trick that triggers an awareness of God – something that can only be stably achieved by years of meditation, prayer and love. Of course that can be observed scientifically by studying our brains under both shrooms or meditation. But the ultimate source of that feeling of universal beneficence that seems calculated to make humans the happiest and kindest they can be remains a mystery. Perhaps it’s all neurons and chemicals – but if they are part of God too, that argument fails.
But why a mushroom? Beats me. A random part of the physical universe that acts like a key to a specifically human spiritual lock: it does seem bizarre. But humans discovered it aeons ago; and the notion of sacramental faith makes space for it, from a Catholic perspective. We eat and drink the divine – as so many faith traditions have for millennia. As long as we don’t mistake the thing for the Godhead, we are merely offered a chance to glimpse what godliness and mindfulness can be. And it remains with us months and years later – actually helping us to attain the calm and peace that true faith generates. Which makes it less a trick than a sacrament – as, by the way, peyote long has been on this continent.
I believe we are indeed all neurons and chemicals. But when all these fall away, God is still with us; and God is us. It is the falling away, the lifting of the veil, that is hard.
(Photo of Psilocybe Cubensis by Flickr user afgooey74)

That is an irrational conclusion, in fact. If I begin to imagine that the voices coming out of my cell phone originate in the cell phone, and dismiss the idea that there are other people in some distant unseen part of the universe talking to me through my cell phone as madness, it is I who am becoming mad. And scientific materialists who imagine that all God-experiences merely originate in the brain because they can be associated with brain phenomena, are similarly mad, and missing the point.
from inside the brain with a voice emanating from a cell phone is completely flawed. Of course a reasonable person would not believe that the voice originates from the cell phone, because a person using a cell phone knows that he or she is talking to another person. We know this by common sense and because we have used cell phones before.
and when someone is tripping balls they can easily experience that chasm, commonly resulting in a radically spiritual effect. Psychotropics allow for this because they allow one to experience how deeply brain states shape reality, that we will never have complete, direct, or as Kant would put it, “pure” access to “things in themselves.”