“The mystic too full of God to speak intelligibly to the world.”

IRC discussion at Scifi.com (1 November 1996) http://web.archive.org/web/20021201214228/http://www.scifi.com/transcripts/aclarke.txt with Clarke and Gentry Lee
1990s

Max Weber, , 1916.
Context: Mysticism intends a state of "possession," not action, and the individual is not a tool but a "vessel" of the divine. Action in the world must thus appear as endangering the absolutely irrational and other-worldly religious state. Active asceticism operates within the world; rationally active asceticism, in mastering the world, seeks to tame what is creatural and wicked through work in a worldly "vocation" (inner-worldly asceticism). Such asceticism contrasts radically with mysticism, if the latter draws the full conclusion of fleeing from the world (contemplative flight from the world). The contrast is tempered, however, if active asceticism confines itself to keeping down and to overcoming creatural wickedness in the actor's own nature. For then it enhances the concentration on the firmly established God-willed and active redemptory accomplishments to the point of avoiding any action in the orders of the world (asceticist flight from the world). Thereby active asceticism in external bearing comes close to contemplative flight from the world. The contrast between asceticism and mysticism is also tempered if the contemplative mystic does not draw the conclusion that he should flee from the world, but, like the inner-worldly asceticist, remain in the orders of the world (inner-worldly mysticism).
In both cases the contrast can actually disappear in practice and some combination of both forms of the quest for salvation may occur. But the contrast may continue to exist even under the veil of external similarity. For the true mystic the principle continues to hold: the creature must be silent so that God may speak.

Variant: The problem with the world is that the intelligent people are full of doubts, while the stupid ones are full of confidence.

Often paraphrased as "The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts."
Compare: "One of the painful things about our time is that those who feel certainty are stupid, and those with any imagination and understanding are filled with doubt and indecision." B. Russell, New Hopes for a Changing World (1951). Compare also: "The best lack all conviction, while the worst / Are full of passionate intensity." W. B. Yeats, The Second Coming (1919).
See also: Dunning-Kruger effect, Historical Antecedents https://en.wikipedia.org/wiki/Dunning–Kruger_effect#Historical_antecedents.
1930s, Mortals and Others (1931-35)

Interview with Suzie Daggett at Insight: Healthy Living (July 2006).
Context: Mystics, contrary to religionists, are always saying that reality is not two things — God and the world — but one thing, consciousness. It is a monistic view of reality based on consciousness that mystics claim to directly intuit. The problem with science has always been that most scientists believe that science must be done within a different monistic framework, one based on the primacy of matter. And then, quantum physics showed us that we must change that myopic prejudice of scientists, otherwise we cannot comprehend quantum physics. So now we have science within consciousness, a new paradigm of science based on the primacy of consciousness that is gradually replacing the old materialist science. Why? Not only because you can't understand quantum physics without this new metaphysics but also because the new paradigm resolves many other paradoxes of the old paradigm and explains much anomalous data.

Address to the Society for Psychical Research (1897)
Context: The clock runs down. I lift the weight by exerting the proper amount of energy, and in this action the law of conservation of energy is strictly obeyed. But now I have the choice of either letting the weight fall free in a fraction of a second, or, constrained by the wheelwork, in twenty-four hours. I can do which I like, and whichever way I decide, no more energy is developed in the fall of the weight. I strike a match; I can use it to light a cigarette or to set fire to a house. I write a telegram; it may be simply to say I shall be late for dinner, or it may produce fluctuations on the stock exchange that will ruin thousands. In these cases the actual force required in striking the match or in writing the telegram is governed by the law or conservation of energy; but the vastly more momentous part, which determines the words I use or the material I ignite, is beyond such a law. It is probable that no expenditure of energy need be used in the determination of direction one way more than another. Intelligence and free will here come into play, and these mystic forces are outside the law of conservation of energy as understood by physicists.

Nobel Prize autobiography (1998)
Context: The world is full of intelligent, well-meaning people who, for one reason or another, did not attend university but are nonetheless well-read and educated. Out there on the prairie lost opportunities of youth were the rule rather than the exception, and I slowly became disabused of the myth of the Bright Young Thing and have not believed in it since.

Lachesis Lapponica: Or, A Tour in Laplan http://books.google.es/books?id=vQ5XAAAAMAAJ&printsec=frontcover&hl=es#v=onepage&q&f=false (1811), translated by James Edward Smith, Lulea, p. 238.