Background

William Stanley Jevons was born on September 1, 1835, in Liverpool, Lancashire, England, the ninth of eleven children. His father, Thomas, was a notable iron merchant with an inventive trait, and his mother, Mary Anne Roscoe, belonged to an old Liverpool family of bankers and lawyers with a literary bent. He was a timid, clever boy and not narrowly studious, showing unusual mechanical aptitude.

Education

At the age of fifteen Jevons was sent to London to attend the University College School. Around this time, he seemed to have formed the belief that he was capable of important achievements as a thinker. At University College, London, he took science courses, and his prowess in chemistry was such that he was recommended, while still an undergraduate and only eighteen years of age, for the job of assayer at the newly established Australian mint. In part to help ease a shrunken family budget, he decided to interrupt his education and to accept the post, which carried the handsome remuneration of over £600 a year. In Sydney, he cultivated his interests in meteorology, botany, and geology and published papers in these fields. After five years he renounced a prosperous future in Australia and went back to England to further his education with a view to becoming an academic; he was already saying that "my forte will be found to lie in the moral and logical sciences."

The first subject Jevons concentrated on was the political economy, which he felt he could transform. His early and sustained interest in economics must have owed something to two disjoint features of his youth: a family bankruptcy caused by a trade slump, and his having been involved in the physical creation of money. The fluctuations of the national economy always fascinated him.

Jevons earned his master’s degree at University College in 1863.

Career

In 1863 Jevons was appointed a junior lecturer at Owens College, Manchester, thus beginning a long association with that city. Two years later he became a part-time professor of logic and political economy at Queen’s College, Liverpool, and in 1866 the Manchester institution raised him to a full-time double professorship of logic and mental and moral philosophy, and of political economy.

In 1876, tired of his teaching chores, Jevons moved to a less onerous but more prestigious professorship at University College. Four years later, he resigned, anxious to spend all his time writing, but his health had begun to deteriorate, despite many long recuperative vacations in England and Norway. A few weeks before his forty-seventh birthday he drowned (possibly as the result of a seizure) while swimming off the Sussex coast.

Whether economics or the rationale of scientific methodology benefited more from Jevons' attention is still arguable, but it was certainly as an economist that he became a public figure. Ironically, his popular fame rested on two achievements that now seem slight or even misguided. The first was his book The Coal Question (1865), a homily about dwindling English fuel supplies in relation to rocketing future demands. The work was Malthusian in the sense that he discussed industry and coal in much the terms that the earlier author had discussed population and food. It was a tract and obviously, as Keynes remarked, épatant. Gladstone, then chancellor of the Exchequer, was deeply impressed by the book, whose "grave conclusions" influenced his fiscal policy. A royal commission was subsequently appointed to look into the matter. Jevons' second achievement was the thesis, developed in the late 1870s from tentative suggestions made by earlier writers, that trade cycles could be correlated with sunspot activity through agrometeorology and, at a further remove, through the price of wheat. It was an ingenious and inherently plausible argument, but the data could not be manipulated to yield convincing evidence and the theory has no standing today.

Achievements

• William Stanley Jevons was a prolific writer, and at the time of his death was a leader in the United Kingdom both as a logician and as an economist. He marked the opening of a new period in the history of economic thought. He also received public recognition for his work on The Coal Question, in which he called attention to the gradual exhaustion of Britain's coal supplies and also put forth the view that increases in energy production efficiency leads to more, not less, consumption. Jevons' various textbooks on logic sold widely for many decades, and his Elementary Lessons in Logic was still in print in 1972. His biggest and most celebrated book, The Principles of Science, is firmly rooted in Jevonian logic and contains practically all his ideas on, and contributions to, the subject.
  
  Alfred Marshall said of his work in economics that it "will probably be found to have more constructive force than any, save that of Ricardo, that has been done during the last hundred years."
  
  Jevons's theory of induction has continued to be influential: "Jevons's general view of induction has received a powerful and original formulation in the work of a modern-day philosopher, Professor K. R. Popper."
  
  His logic piano earned much acclaim, especially after its exhibition at the Royal Society in 1870. At present it is on display in the Oxford Museum of the History of Science. Although its principal value was as an aid to the teaching of the new logic of classes and propositions, it actually solved problems with superhuman speed and accuracy, and some of its features can be traced in modern computer designs.

Works

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• book

  • The Progress of the Mathematical Theory of Political Economy 1862
  • A Serious Fall in the Value of Gold Ascertained, and Its Social Effects Set Forth: With Two Diagrams 1863
  • Pure Logic: Or, the Logic of Quality Apart From Quantity 1864
  • The Coal Question 1865
  • The substitution of similars, the true principle of reasoning, derived from a modification of Aristotle's dictum 1869
  • Elementary Lessons in Logic 1870
  • The Match Tax: A Problem of Finance 1871
  • The Theory of Political Economy 1871
  • The Principles of Science 1874
  • Money and the Mechanism of Exchange 1875
  • A Primer on Political Economy 1878
  • Studies in Deductive Logic 1880
  • The State in Relation to Labour 1882
  • Methods of Social Reform and Other Papers 1883
  • Investigations in Currency and Finance 1884
  • Letters and Journal of W. Stanley Jevons 1886
  • Papers and Correspondence of William Stanley Jevons 1972

Religion

Jevons was brought up, and always in spirit remained a Unitarian.

Views

Jevons brought to economic theory a fruitful insistence on a mathematical framework with an abundance of statistical material to fill out the structure. He was a diligent collector and sifter of statistics, and his methods of presenting quantitative data showed insight and skill. He strongly advocated the use of good charts and diagrams, which, he said, were to the economist what fine maps are to the geographer. He clarified certain concepts, particularly that of value, which he regarded as a function of utility, a property he wrote about with luminance.

Utility, said Jevons, "is a circumstance of things arising out of their relation to man’s requirements and that normally diminishes." One of his favorite examples concerns bread, a daily pound of which, for a given person, has the "highest conceivable utility," and he went on to show that extra pounds have progressively smaller utilities, illustrating that the "final degree of utility" declines as consumption rises. This simple proposition was quite new, for the classical theorists, including Marx, had analyzed value from the supply side only, whereas Jevons' analysis was from demand. Later writers were to recognize the necessity of both approaches. Incidentally, Jevons' approach was the forerunner of the idea of "marginal utility," the first of the "marginal" concepts on which modern economics may be said to rest.

Although some of Jevons' ideas can be found inchoate in the works of his predecessors Augustus Cournot and H. H. Gossen, and of his contemporaries Karl Menger and Leon Walras, he arrived at his theories independently and can be seen as a pathbreaker in modern economics. His stress on the subject as essentially a mathematical science was judicious, and he held no exaggerated notions about the role of mathematics - he had observed, he said slyly, that mathematical students were no better than any others when faced with real-life problems.

Economics and logic have traditionally been associated in England, and Jevons belongs to the chain of distinguished thinkers, from John Stuart Mill to Frank Ramsey, who are linked to both disciplines. He was opposed to Mill in divers particulars, and at times he looked upon the older man's deep influence on the teaching of logic as hardly short of disastrous. Mill's mind, he once averred, was "essentially illogical," and Jevons eagerly seized on Boole's remarkable new symbolic logic to show up what he deemed the vastly inferior warmed-over classical logic of Mill. Jevons actually improved on Boole in some important details, as, for instance, in showing that the Boolean operations of subtraction and division were superfluous. Whereas Boole had stuck to the mutually exclusive "either-or," Jevons redefined the symbol + to mean "either one, or the other, or both." This change, which was at once accepted and became permanent, made for greater consistency and flexibility. The expression a + a, which was an uninterpretable nuisance in the Boolean scheme, now fell into place, the sum being a.

At the same time Jevons deprecated certain aspects of Boole’s work. He thought it too starkly symbolic and declared that "the mathematical dress into which he threw his discoveries is not proper to them, and his quasi-mathematical processes are vastly more complicated than they need have been" - an extravagant statement, even in the light of Jevons' own logic. Indeed, some of Jevons' writings about Boole’s system, and especially his worries about the discrepancies between orthodox and Boolean algebras, suggest that he did not fully grasp Boole’s originality, potential, and abstractness. Nevertheless, he can certainly be reckoned a leading propagandist for Boole, particularly among those who could not understand, or who would not brook, Boole’s logic. Moreover, Jevons was led through Boole’s ideas to some original work on a logical calculus.

Jevons' logic of inference was dominated by what he called the substitution of similars, which expressed "the capacity of mutual replacement existing in any two objects which are like or equivalent to a sufficient degree." This became for him "the great and universal principle of reasoning" from which "all logical processes seem to arrange themselves in simple and luminous order." It also allowed him to develop a special equational logic, with which he constructed various truth-tablelike devices for handling logical problems. He did not foresee that a truth-table calculus could be developed as a self-contained entity, but he was able to devise a logic machine - a sort of motional form of the later diagrammatic scheme of John Venn. Jevons' "logical piano" was built for him by a Salford clockmaker. It resembled a small upright piano, with twenty-one keys for classes and operations in an equational logic. Four terms, A, B, C, and D, with their negations, in binary combinations, were displayed in slots in front and in back of the piano; and the mechanism allowed for classification, retention, or rejection, depending upon what the player fed in via the keyboard. The keyboard was arranged in an educational form, with all eight terms on both left and right and a "copula" key between them. The remaining four keys were, on the extreme left, "finis" and the inclusive "or," and, on the extreme right, "full stop" and the inclusive "or again." In all 216 (65,536) logical selections were possible.

Inescapably, the matter of induction, the basis of the scientific method and the bugbear of scientific philosophy, is lengthily explored and analyzed. Jevons confidently declared that "induction is, in fact, the inverse operation of deduction." Such a statement - in one sense a truism and in another a travesty - might be thought a feeble beginning for a study of the how and why of science, but Jevons acquits himself admirably. He does not confuse the formal logic of induction with the problems of inductive inference in the laboratory, and he is obviously under no illusions about the provisional nature of all scientific "truth."

Jevons was perhaps the first writer to insist that absolute precision, whether of observation or of correspondence between theory and practice, is necessarily beyond human reach. Taking a thoroughly modern position, Jevons held that approximation was of the essence, adding that "in the measure of continuous quantity, perfect correspondence must be accidental, and should give rise to suspicion rather than to satisfaction." He also felt that causation was overrated if the not dangerous concept in science and that what we seek are logically significant interrelations. All the while, he said, the scientist is framing hypotheses, checking them against existing information, and then designing experiments for further support. There can be no cut-and-dried conclusion to most investigations and no guarantee that correct answers can be issued. The scientist must act in accordance with the probabilities associable with rival hypotheses, which probabilities, or, as many would prefer to say today, likelihoods, constitute the decision data. Thus "the theory of probability is an essential part of logical method, so that the logical value of every inductive result must be determined consciously or unconsciously, according to the principles of the inverse method of probability." An entire chapter of The Principles is devoted to direct probability and another to inverse probability.

As a probabilist, Jevons was fundamentally a disciple of Laplace, or at least of Laplace as reshaped by Jevons' own college teacher and mentor Augustus De Morgan - that is to say, he was a subjectivist. Probability, he maintained, "belongs wholly to the mind" and "deals with quantity of knowledge." Yet he was careful to emphasize that probability is to be taken as a measure, not of an individual’s belief, but of rational belief - of what the perfectly logical man would believe in the light of the available evidence. In espousing this view, Jevons sidestepped Boole's disturbing reservations about subjectivism - mainly because he had difficulty grasping them. In general, Jevons was silent about the movement toward a frequential theory of probability that was growing out of the work of Leslie, Ellis, and Poisson, as well as that of his contemporary, Venn.

To the modern reader, however, Jevons may seem altogether too self-assured in this notoriously treacherous field. For example, he wholeheartedly accepted Laplace’s controversial rule of succession and offered a naive illustration of its applicability. To the frequentist, insistent on a clearly delineated sample space, this statement is almost wholly devoid of meaning. Another, more bizarre example of his naive Laplaceanism is his contention that the proposition "a platythliptic coefficient is positive" has, because of our complete ignorance, a probability of correctness of 1/2. Curiously, in discoursing on what he calls "the grand object of seeking to estimate the probability of future events from past experience," Jevons made only one casual and unenlightening reference to Thomas Bayes, who, a century earlier, had been the first to attempt a coherent theory of inverse probability.

Quotations: "You will perceive that economy, scientifically speaking, is a very contracted science; it is in fact a sort of vague mathematics which calculates the causes and effects of man's industry, and shows how it may be best applied."

"When quite young I can remember I had no thought or wish of surpassing others. I was rather taken with a liking of little arts and bits of learning."

"Facts are valueless unless connected and explained by a correct theory; analogies are very dangerous grounds of inference, unless carefully founded on similar conditions; experience misleads if it is misinterpreted."

"In matters of philosophy and science authority has ever been the great opponent of truth. A despotic calm is usually the triumph of error. In the republic of the sciences sedition and even anarchy are beneficial in the long run to the greatest happiness of the greatest number."

"A correct theory is the first step towards improvement, by showing what we need and what we might accomplish."

"To me it is far more pleasant to agree than to differ; but it is impossible that one who has any regard for truth can long avoid protesting against doctrines which seem to him to be erroneous. There is ever a tendency of the most hurtful kind to allow opinions to crystallise into creeds."

"Truth indeed is sacred; but, as Pilate said, 'What is truth?' Show us the undoubted infallible criterion of absolute truth, and we will hold it as a sacred inviolable thing. But in the absence of that infallible criterion, we have all an equal right to grope about in our search of it, and no body and no school nor clique must be allowed to set up a standard of orthodoxy which shall bar the freedom of scientific inquiry."

"I protest against deference to any man, whether John Stuart Mill, or Adam Smith, or Aristotle, being allowed to check inquiry. Our science has become far too much a stagnant one, in which opinions rather than experience and reason are appealed to."

Membership

Jevons was made a fellow of the Royal Society in 1872.

• 

  Fellow

  Royal Society , United Kingdom

  1872 - 1882

Personality

Although Jevons spent more than ten years teaching, he considered himself a poor lecturer, and also hated to speak in public.

Jevons had a strong and almost visionary sense of his own destiny as a thinker, and he worried about its fulfillment. A prodigious worker, he sustained many side interests and was passionately fond of music. He tried hard and successfully to improve his literary style, and his later writings are more concise and readable than his earlier ones.

Quotes from others about the person

• Michael J. Beeson: "William Stanley Jevons heard of Boole's work, and undertook to build a machine to make calculations in Boolean algebra. He successfully designed and built such a machine, which he called the Logical Piano, apparently because it was about the size and shape of a small piano. This machine and its creator deserve much more fanfare than they have so far received. This was the first machine to do mechanical inference."

Interests

• music, writing

Connections

In 1864 Jevons married Harriet Ann Taylor, the daughter of the founder and first editor of the Manchester Guardian, and the couple was soon enjoying the lively intellectual atmosphere of Victorian Manchester. They had three children, of whom one, Herbert Stanley, became a well-known economist.

Father:

Thomas Jevons

Mother:

Mary Anne Roscoe

Spouse:

Harriet Ann Taylor

Sister:

Jane Emily Jevons

Brother:

Roscoe Jevons

Sister:

Lucy Anne Jevons

Brother:

Herbert Jevons

Sister:

Mary Emily Jevons

Brother:

Charles Thomas Jevons

Brother:

Edward Griffies Jevons

Sister:

Henrietta Elizabeth Jevons

Brother:

Thomas Edwin Jevons

Son:

Herbert Stanley Jevons

Daughter:

Harriet Winefred Jevons

Daughter:

Lucy Cecelia Jevons

References

• Dictionary of Scientific Biography, Volume 7
  1973