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William Kingdon Clifford citáty
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William Kingdon Clifford byl anglický matematik a filosof.

Vystudoval matematiku na King’s College v Londýně a Trinity College v Cambridge. Nakonec, roku 1871, se stal profesorem na University College v Londýně. Roku 1874 byl zvolen členem Královské společnosti

Inspirován pracemi Bernharda Riemanna a Nikolaje Lobačevského věnoval velkou pozornost neeuklidovské geometrii. Roku 1876 napsal přelomový článek On the space theory of matter, kde vyjádřil myšlenku, že energie a hmota jsou pouze různá zakřivení vesmíru. To bývá považováno za předstupeň teorie relativity.

Významně přispěl také ke studiu algebry. Především tím, když zavedl tzv. bikvaterniony , jež byly zobecněním kvaternionů Williama Rowana Hamiltona. Užíval je k popisu pohybu v neeukleidovských prostorech i po některých eukleidovských plochách. Později navázal na studie Hermanna Grassmanna o tzv. vnějších algebrách. Definoval obecnější typy algeber, tyto se po něm dnes nazývají Cliffordovy algebry.

Ve filozofii měl blízko k Hermannu von Helmholtzovi a Ernstu Machovi. Proslul pojmy „látka mysli“ , která označuje základní komponenty, z nichž se má skládat vědomí, a „kmenové já“ . Pokusil se též poukázat na některé vztahy kantovské filozofie a neuklidovské geometrie.

Zemřel v 33 letech na tuberkulózu. Většina jeho prací byla vydána až posmrtně, péčí Karla Pearsona. Wikipedia  

✵ 4. květen 1845 – 3. březen 1879
William Kingdon Clifford foto
William Kingdon Clifford: 48 citátů0 lajků

William Kingdon Clifford: Citáty anglicky

“Then he should have no time to believe.”

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William Kingdon Clifford

The Ethics of Belief (1877), The Duty of Inquiry
Kontext: Inquiry into the evidence of a doctrine is not to be made once for all, and then taken as finally settled. It is never lawful to stifle a doubt; for either it can be honestly answered by means of the inquiry already made, or else it proves that the inquiry was not complete.
"But," says one, "I am a busy man; I have no time for the long course of study which would be necessary to make me in any degree a competent judge of certain questions, or even able to understand the nature of the arguments."
Then he should have no time to believe.

“If an event really happened which was not a part of the uniformity of nature, it would have two properties: no evidence could give the right to believe it to any except those whose actual experience it was; and no inference worthy of belief could be founded upon it at all.
Are we then bound to believe that nature is absolutely and universally uniform? Certainly not; we have no right to believe anything of this kind. The rule only tells us that in forming beliefs which go beyond our experience, we may make the assumption that nature is practically uniform so far as we are concerned. Within the range of human action and verification, we may form, by help of this assumption, actual beliefs; beyond it, only those hypotheses which serve for the more accurate asking of questions.”

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William Kingdon Clifford

The Ethics of Belief (1877), The Limits Of Inference

“Upon Clifford's death the labour of revision and completion was entrusted to Mr. R. C. Rowe, then Professor of Pure Mathematics at University College, London. …On the sad death of Professor Rowe, in October 1884, I was requested… to take up the task of editing… For the latter half of Chapter III. and for the whole of Chapter IV. …I am alone responsible. Yet whatever there is in them of value I owe to Clifford; whatever is feeble or obscure is my own. …With Chapter V. my task has been by no means light. …Without any notice of mass or force it seemed impossible to close a discussion on motion; something I felt must be added. I have accordingly introduced a few pages on the laws of motion. I have since found that Clifford intended to write a concluding chapter on mass. How to express the laws of motion in a form of which Clifford would have approved was indeed an insoluble riddle to me, because I was unaware of his having written anything on the subject. I have accordingly expressed, although with great hesitation, my own views on the subject; these may be concisely described as a strong desire to see the terms matter and force, together with the ideas associated with them, entirely removed from scientific terminology—to reduce, in fact, all dynamic to kinematic. I should hardly have ventured to put forward these views had I not recently discovered that they have (allowing for certain minor differences) the weighty authority of Professor Mach, of Prag. But since writing these pages I have also been referred to a discourse delivered by Clifford at the Royal Institution in 1873, some account of which appeared in Nature, June 10, 1880. Therein it is stated that 'no mathematician can give any meaning to the language about matter, force, inertia used in current text-books of mechanics.”

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William Kingdon Clifford

This fragmentary account of the discourse undoubtedly proves that Clifford held on the categories of matter and force as clear and original ideas as on all subjects of which he has treated; only, alas! they have not been preserved.
Preface by Karl Pearson
The Common Sense of the Exact Sciences (1885)

“The name philosopher, which meant originally 'lover of wisdom,' has come in some strange way to mean a man who thinks it is his business to explain everything in a certain number of large books. It will be found, I think, that in proportion to his colossal ignorance is the perfection and symmetry of the system which he sets up; because it is so much easier to put an empty room tidy than a full one.”

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William Kingdon Clifford

As quoted by A. D'Abro, The Evolution of Scientific Thought from Newton to Einstein https://archive.org/details/TheEvolutionOfScientificThought (1927)

“Riemann has shewn that as there are different kinds of lines and surfaces, so there are different kinds of space of three dimensions; and that we can only find out by experience to which of these kinds the space in which we live belongs. In particular, the axioms of plane geometry are true within the limits of experiment on the surface of a sheet of paper, and yet we know that the sheet is really covered with a number of small ridges and furrows, upon which (the total curvature not being zero) these axioms are not true. Similarly, he says although the axioms of solid geometry are true within the limits of experiment for finite portions of our space, yet we have no reason to conclude that they are true for very small portions; and if any help can be got thereby for the explanation of physical phenomena, we may have reason to conclude that they are not true for very small portions of space.”

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William Kingdon Clifford On the Space-Theory of Matter

Abstract
On the Space-Theory of Matter (read Feb 21, 1870)

“I hold in fact
(1) That small portions of space are in fact of a nature analogous to little hills on a surface which is on the average flat; namely, that the ordinary laws of geometry are not valid in them.
(2) That this property of being curved or distorted is continually being passed on from one portion of space to another after the manner of a wave.
(3) That this variation of the curvature of space is what really happens in that phenomenon which we call the motion of matter, whether ponderable or etherial.
(4) That in the physical world nothing else takes place but this variation, subject possibly to the law of continuity.”

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William Kingdon Clifford On the Space-Theory of Matter

Abstract
On the Space-Theory of Matter (read Feb 21, 1870)

“We have no reason to fear lest a habit of conscientious inquiry should paralyse the actions of our daily life.
But because it is not enough to say, "It is wrong to believe on unworthy evidence," without saying also what evidence is worthy, we shall now go on to inquire under what circumstances it is lawful to believe on the testimony of others; and then, further, we shall inquire more generally when and why we may believe that which goes beyond our own experience, or even beyond the experience of mankind.”

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William Kingdon Clifford

The Ethics of Belief (1877), The Weight Of Authority

“The goodness and greatness of a man do not justify us in accepting a belief upon the warrant of his authority, unless there are reasonable grounds for supposing that he knew the truth of what he was saying. And there can be no grounds for supposing that a man knows that which we, without ceasing to be men, could not be supposed to verify.”

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William Kingdon Clifford

The Ethics of Belief (1877), The Weight Of Authority

“I am endeavouring in a general way to explain the laws of double refraction on this hypothesis, but have not yet arrived at any results sufficiently decisive to be communicated.”

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William Kingdon Clifford On the Space-Theory of Matter

On the Space-Theory of Matter (read Feb 21, 1870)

“In March 1879 Clifford died at Madeira; six years afterwards a posthumous work is for the first time placed before the public. …The original work as planned by Clifford was to have been entitled The First Principles of the Mathematical Sciences Explained to the Non-Mathematical, and to have contained six chapters, on Number, Space, Quantity, Position, Motion, and Mass respectively. Of the projected work Clifford in the year 1875 dictated the chapters on Number and Space completely, the first portion of the chapter on Quantity, and somewhat later nearly the entire chapter on Motion. The first two chapters were afterwards seen by him in proof, but never finally revised. Shortly before his death he expressed a wish that the book should only be published after very careful revision and that its title should be changed to The Common Sense of the Exact Sciences.”

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William Kingdon Clifford

Preface by Karl Pearson
The Common Sense of the Exact Sciences (1885)

“Other qualities of bodies are connected with simple energy of motion and energy of position. Such is heat, which we find by experiment can be turned into work. Finding it convertible with energy, we call it a form of energy. ...But as to heat, it is further established by experiment that in this case the energy of motion does really persist as such. Thus a gas consists of molecules flying about with velocity, rotating and vibrating, and so having energy motion. All this energy of motion is what we call heat, and thus heat is a repetition of a known meaning of energy. Again, heat exists between a radiating body and the thing it warms; now the intermediate space is filled by the luminiferous ether, which, being elastic, has in its ultimate parts both energy of motion energy of position. In these forms the heat exists in the space in question.”

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William Kingdon Clifford

"Energy and Force" (Mar 28, 1873)

“When a body is let fall from a higher position to lower one, it has, at the instant when it is let go, energy of motion; but it gains, in falling, as much energy of motion as it loses energy of position. It is found that the sum of energy of motion and energy of position is always constant. ...Energy is a quantity which can be greater or less but has no direction. ...This constancy is expressed by including them in common name of Energy, and saying that energy is conserved, or is indestructible. This form of speech might be applied to other cases of alternate immortality, where one of two things comes into existence on disappearance of the other.”

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William Kingdon Clifford

"Energy and Force" (Mar 28, 1873)

“Momentum may be roughly described as quantity motion. A body moving at a speed of say twenty an hour, has a certain quantity of motion. If the body goes forty miles an hour there is twice as motion; or if twice as much matter goes twenty miles hour, there is also twice as much motion. Momentum is measured by the quantity of matter moving at a rate mass \times velocity.”

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William Kingdon Clifford

"Energy and Force" (Mar 28, 1873)

“I specially wish you not to go away with the idea that the exercise of scientific thought is properly confined... When the Roman jurists applied their experience of Roman citizens to dealings between citizens and aliens, showing by the difference of their actions that they regarded the circumstances as essentially different, they laid the foundations of that great structure which has guided the social progress of Europe. That procedure was an instance of strictly scientific thought. When a poet finds that he has to move a strange new world which his predecessors have not moved; when, nevertheless, he catches fire from their flashes, arms from their armoury, sustentation from their foot-prints, the procedure by which he applies old experience to new circumstances is nothing greater or less than scientific thought. When the moralist studying the conditions of society and the ideas of right and wrong which have come down to us from a time when war was the normal condition of man and success in war the only chance of survival, evolves from them the conditions and ideas which must accompany a time of peace, when the comradeship of equals is the condition of national success; the process by which he does this is scientific thought and nothing else.”

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William Kingdon Clifford

Zdroj: "On the Aims and Instruments of Scientific Thought" (Aug 19, 1872), pp. 156-157.

“Force is not a fact at all, but an idea embodying what is approximately the fact.”

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William Kingdon Clifford

Preface footnote, p. ix. Mr. R. Tucker searched Clifford's note books for Karl Pearson and sent him the above quote, in Clifford's handwriting.
The Common Sense of the Exact Sciences (1885)

“Energy is of two kinds: 1. Energy of motion; 2. Energy of position.”

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William Kingdon Clifford

"Energy and Force" (Mar 28, 1873)

“Force, defined as above, is not conserved at all. It may appear and disappear; it is continually being created and destroyed. "Conservation of force" is, mathematically speaking, a contradiction in terms.”

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William Kingdon Clifford

"Energy and Force" (Mar 28, 1873)

“No mathematician can give any meaning to language about matter, force, inertia, used in text-books of mechanics.”

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William Kingdon Clifford

"Energy and Force" (Mar 28, 1873)

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