Bergson and the Brain: The Philosophical Engine

“Huxley borrowed the reducing valve from Bergson, borrowed the C.D. Broad citation to give it academic credibility, and built the central neuroscientific argument of his era without any neuroscience.”

Henri Bergson proposed in 1896 that the brain's primary function was not to produce consciousness but to filter it. Most of what the mind could perceive is suppressed in the interests of practical action, what makes it through is the small portion relevant to survival and social functioning. The rest is excluded.

Aldous Huxley read this proposition and recognized it as the theoretical foundation for something he'd experienced in a Los Angeles living room in May 1953. He quoted C.D. Broad's sympathetic commentary on Bergson's argument, gave the mechanism a name, the reducing valve, and built The Doors of Perception's central claim: that mescaline works by impairing the brain's filtering function, allowing more of Mind at Large into awareness.

Huxley had no neuroscience to support this. The tools didn't exist. Brain imaging was decades away. What he had was philosophical precision and the quality of the experience itself, which felt exactly like what the reducing valve model predicted it should feel like.

Sixty-five years later, neuroscientist Robin Carhart-Harris and mathematician Karl Friston published the REBUS model: Relaxed Beliefs Under Psychedelics. Their proposal, derived from predictive coding theory and supported by fMRI data, describes psychedelics as reducing the 'precision weighting' of top-down priors, the brain's predictions about what it's about to perceive. When those predictions are weighted less heavily, bottom-up sensory information enters awareness in greater abundance and with less pre-processing.

This is Bergson's reducing valve, translated into the vocabulary of computational neuroscience. The mechanism Huxley described intuitively in 1954, impairment of the brain's filtering function, resulting in richer but less practically organized perceptual experience, maps precisely onto what contemporary neuroscience has verified experimentally.

Huxley borrowed the reducing valve from Bergson, borrowed the C.D. Broad citation to give it academic credibility, and built the central neuroscientific argument of the psychedelic literature without any neuroscience. The argument was correct. That's either very good philosophy or very good luck.

Sources

• Huxley, The Doors of Perception (1954)
• Carhart-Harris & Friston, Pharmacological Reviews (2019)
• Bergson, Matter and Memory (1896)