"Science is a religion of skepticism. To escape from the microcosm of our childhood experience, from the microcosm of our culture and its dogmas, from the half truths our parents told us, it is essential that we be skeptical about what we think we have learned to date. It is the scientific attitude that enables us to transform our personal experience of the microcosm into a personal experience of the macrocosm.The road of spiritual growth begins by distrusting what we already believe, by actively seeking the threatening and unfamiliar, by deliberately challenging the validity of what we have previously been taught and hold dear. We must begin by becoming scientists."

- M. Scott Peck, "A Road Less Travelled"

More of the brain is involved in perception and response to music than to language, or anything else. - Oliver Sacks

The function of the brain and nervous system and sense organs is in the main eliminative and not productive.

- Henri Bergson

There are two states in which man arrives at the rapturous feeling of existence, namely in dreaming and in intoxication.
- Nietzsche, The Dionysian Worldview,

By wine or opium we can intensify and considerably heighten our mental powers, but as soon as the right measure of stimulus is exceeded, the effect will be exactly the opposite.

- Schopenhauer

Without the eye there can be no sensations of vision, and without the brain there could be no recollected visible ideas; but neither the optic nerve nor the brain can be considered as the percipient principle—they are but the instruments of a power which has nothing in common with them. …

The desire of glory, of honour, of immortal fame, and of constant knowledge, so usual in young persons of well-constituted minds, cannot, I think, be other than symptoms of the infinite and progressive nature of intellect.

- Humphry Davy, from Consolations in Travel or The Last Days of a Philosopher

Humphry Davy on laughing gas (nitrous oxide):

"I lost all connection with external things; trains of vivid visible images passed through my mind and were connected with words in such a manner as to produce perceptions perfectly novel. I existed in a world of newly connected and newly modified ideas … I exclaimed to Dr Kinglake, “Nothing exists but thoughts!” …

I have often felt very great pleasure when breathing it alone, in darkness and silence, occupied only by ideal existence."