09 May 2019

On Proofs (1975 - 1989)

“The conception of the mental construction which is the fully analysed proof as being an infinite structure must, of course, be interpreted in the light of the intuitionist view that all infinity is potential infinity: the mental construction consists of a grasp of general principles according to which any finite segment of the proof could be explicitly constructed.” (Michael Dummett, “The philosophical basis of intuitionistic logic”, 1975)

“No theory ever agrees with all the facts in its domain, yet it is not always the theory that is to blame. Facts are constituted by older ideologies, and a clash between facts and theories may be proof of progress. It is also a first step in our attempt to find the principles implicit in familiar observational notions.”  (Paul K Feyerabend, “Against Method: Outline of an Anarchistic Theory of Knowledge”, 1975)

“There is an infinite regress in proofs; therefore proofs do not prove. You should realize that proving is a game, to be played while you enjoy it and stopped when you get tired of it.” (Imre Lakatos, “Proofs and Refutations”, 1976)

“On the face of it there should be no disagreement about mathematical proof. Everybody looks enviously at the alleged unanimity of mathematicians; but in fact there is a considerable amount of controversy in mathematics. Pure mathematicians disown the proofs of applied mathematicians, while logicians in turn disavow those of pure mathematicians. Logicists disdain the proofs of formalists and some intuitionists dismiss with contempt the proofs of logicists and formalists.” (Imre Lakatos, “Mathematics, Science and Epistemology” Vol. 2, 1978)

"Mathematics is a way of finding out, step by step, facts which are inherent in the statement of the problem but which are not immediately obvious. Usually, in applying mathematics one must first hit on the facts and then verify them by proof. Here we come upon a knotty problem, for the proofs which satisfied mathematicians of an earlier day do not satisfy modem mathematicians." (John R Pierce, "An Introduction to Information Theory: Symbols, Signals & Noise" 2nd Ed., 1980)

"Mathematicians start out with certain assumptions and definitions, and then by means of mathematical arguments or proofs they are able to show that certain statements or theorems are true." (John R Pierce, "An Introduction to Information Theory: Symbols, Signals & Noise" 2nd Ed., 1980)

“When a mathematician asks himself why some result should hold, the answer he seeks is some intuitive understanding. In fact, a rigorous proof means nothing to him if the result doesn’t make sense intuitively.” (Morris Kline, “Mathematics: The Loss of Certainty”, 1980)

“No proof is final. New counterexamples undermine old proofs. The proofs are then revised and mistakenly considered proven for all time. But history tells us that this merely means that the time has not yet come for a critical examination of the proof” (Morris Kline, “Mathematics: The Loss of Certainty”, 1980)

“If the proof starts from axioms, distinguishes several cases, and takes thirteen lines in the text book […] it may give the youngsters the impression that mathematics consists in proving the most obvious things in the least obvious way.” (George Pólya, “Mathematical Discovery: on Understanding, Learning, and Teaching Problem Solving”, 1981)

“A proof transmits conviction from its premises down to its conclusion, so it must start with premises […] for which there already is conviction; otherwise, there will be nothing to transmit.” (Robert Nozick, Philosophical Explanations, 1981)

“We often hear that mathematics consists mainly in ‘proving theorems’. Is a writer’s job mainly that of ‘writing sentences’? A mathematician’s work is mostly a tangle of guesswork, analogy, wishful thinking and frustration, and proof, far from being the core of discovery, is more often than not a way of making sure that our minds are not playing tricks.” (Gian-Carlo Rota, “Complicating Mathematics” in “Discrete Thoughts”, 1981)

“People might suppose that a mathematical proof is conceived as a logical progression, where each step follows upon the ones that have preceded it. Yet the conception of a new argument is hardly likely actually to proceed in this way. There is a globality and seemingly vague conceptual content that is necessary in the construction of a mathematical argument; and this can bear little relation to the time that it would seem to take in order fully to appreciate a serially presented proof” (Roger Penrose, “The Emperor’s New Mind”, 1989)

See also:
Proofs I, II, III, IV, V, VI, VIII, IX
Theorems I, II, III, IV, V, VI, VII, VIII, IX, X

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