Huxley recounts his 1953 mescaline experience and explores visionary states, mysticism and the heavenly and hellish extremes of altered perception.
Ordinary perception is a narrowing: the mind shuts out whole classes of experience because they do nothing to help us survive. Loosen that filter and those excluded impressions flood back in. What we normally see is what an animal obsessed with survival, and a human obsessed with words, needs to see, not how things are.
Dismissing an experience as not truly spiritual because a chemical caused it misses the point. Every experience, including those we call purely intellectual or aesthetic, happens in some chemical state of the body. We call some experiences pure only because we never checked what was going on inside us when they happened.
The same drug can bring bliss or torment depending on the condition of the mind that takes it. Fear, anger, depression or chronic anxiety beforehand tip the experience into hell. Most people get the heavenly version; a minority find only purgatory.
Our fine sense of color is unnecessary for staying alive, so everyday perception leaves us blind to countless shades. When the filter lifts, colors intensify and the finest distinctions become visible. Things we brush aside as secondary qualities may in fact be primary.
When everyday perception falls away, questions of place, distance and position stop mattering, and time shrinks to an endless present. The mind sees instead in terms of how intensely things exist, how deep their meaning runs, and how they fit into patterns. The will to act weakens along with this.