“What was happening in my brain? The notion that there is so much more out there, or in here, that our conscious minds allow us to perceive, is consistent with the neuroscientific concept of predictive coding. According to this theory, our brain admits the minimum amount of information needed to confirm or correct its best guesses as to what is out there, or in the case of our unconscious feelings, in here. This top down predictions of reality and prior beliefs are a bit like maps to sensory and psychological experience, and as long as they represent the actual territory well enough for us to navigate it successfully, there is no need to flood the system with lots of unecessary detail. Natural selection has shaped human concsiousness not necessarily to scrupulously represent reality, but to maximize our survival, admiting only the measly trickle of information needed for us to get by rather than the full spectrum of what there is to perceive and to think. Psychedelics seem to mess with this system in one of two ways. In some cases the brains predictions about reality go haywire as when you see faces in the clouds, or musical notes leap to life, or something happens to convince you your being followed. Common on LSD or psycolcybin, this kind of magical thinking might occur when top down predictions generated by the brain are no longer adequately strained or corrected by bottom up information arriving about the world via the senses, but if Huxley’s account and my experience are representative then something very different happens on the brain on mescaline. Here, the bottom up information of the senses and the emotions inundates our awareness, sweeping away the minds predictions, maps, beliefs, and cozy symbols; all the tools we have for organizing the inner and outer worlds and which feels like a title wave of awe.”