“A true aphorism legitimates itself; whoever feels the need to legitimate an aphorism, admits that it is illegal. The surface of an aphorism should conceal profound truth. The claim that everybody can learn everything is superficial, but is as wrong as it can be. As a matter of fact, it is no aphorism but an advertising slogan, and the excuse that it is an aphorism, is a mere wink: in advertising you cannot do without exaggerating. But even as a wink it does not become more true.”
Hans Freudenthal (1977), Weeding and Sowing: Preface to a Science of Mathematical Education, p. 56
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Hans Freudenthal 27
Dutch mathematician 1905–1990Related quotes
“In an aphorism, aptness counts for more than truth.”
City Aphorisms, Fourth Selection (1987)

“An aphorism can never be the whole truth; it is either a half-truth or a truth-and-a-half.”
Die Fackel no. 270/71 (19 January 1909)
Die Fackel

“Even more than in a poem, it is the aphorism that the word is god.”
Drawn and Quartered (1983)
Splendid Isolation (1980) New Haven: Yale University Press. p. 38

Voltaire, Foreign Review, (1829); compare: "How comes it to pass, then, that we appear such cowards in reasoning, and are so afraid to stand the test of ridicule?", Shaftesbury, Characteristics. A Letter concerning Enthusiasm, sect. 2.; "Truth, 't is supposed, may bear all lights; and one of those principal lights or natural mediums by which things are to be viewed in order to a thorough recognition is ridicule itself", Shaftesbury, Essay on the Freedom of Wit and Humour, sect. 1.; "'T was the saying of an ancient sage [Gorgias Leontinus, apud Aristotle's "Rhetoric," lib. iii. c. 18], that humour was the only test of gravity, and gravity of humour. For a subject which would not bear raillery was suspicious; and a jest which would not bear a serious examination was certainly false wit", ibid. sect. 5.
1820s, Critical and Miscellaneous Essays (1827–1855)

"Gurdjieff" in Man, Myth and Magic : Encyclopedia of the Supernatural (1970) http://www.gurdjieff.org/travers1.htm
Context: It is clear from Gurdjieff's writings that hypnotism, mesmerism and various arcane methods of expanding consciousness must have played a large part in the studies of the Seekers of Truth. None of these processes, however, is to be thought of as having any bearing on what is called Black Magic, which, according to Gurdjieff, "has always one definite characteristic. It is the tendency to use people for some, even the best of aims, without their knowledge and understanding, either by producing in them faith and infatuation or by acting upon them through fear. There is, in fact, neither red, green nor yellow magic. There is "doing." Only "doing" is magic." Properly to realise the scale of what Gurdjieff meant by magic, one has to remember his continually repeated aphorism, "Only he who can be can do," and its corollary that, lacking this fundamental verb, nothing is "done," things simply "happen."

Source: Propaganda & The Ethics Of Persuasion (2002), Chapter Five, Advertising And Public Relations Ethics, p. 176
Source: "The Utility and Futility of Aphorisms," 1863, p. 178.