# Popular Science Monthly/Volume 11/October 1877/Sketch of Professor Jevons

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WILLIAM STANLEY JEVONS.
* SKETCH OF PROFESSOR JEVONS.
WILLIAM STANLEY JEVONS was born at Liverpool, in the year 1835. His father, Thomas Jevons, was an iron-merchant in that city; his mother was a daughter of William Roscoe, the well-known historian. She was a woman of great cultivation, the writer of hymns and poems which are to be found in general collections, and the editor of the "Sacred Offering." Young Jevons received his early education along with his cousin. Prof. Roscoe, at the High-School of the Mechanics' Institution, Liverpool, the head-master of which was, at that time, Dr. W. B. Hodgson, now Professor of Political Economy in the University of Edinburgh. At the age of sixteen he went to University College, London, and, during the two years he remained there, distinguished himself highly in the classes of mathematics and natural science. In 1853 he received, on the recommendation of Prof. Graham, the offer of an appointment as an assayer to the Australian Royal Mint at Sydney. He accepted this appointment, and, after having qualified himself by a course of assaying under Profs. Graham and Miller, he proceeded to Sydney, where he discharged the duties of the office for five years, devoting his leisure time to scientific investigations, particularly meteorology. He, however, resolved to leave this field of work and devote himself to the study of the higher sciences. Returning from Australia, he visited the United States in 1859, and, arriving at London, he at once resumed his studies in the University College, and won distinction in his various classes. In 1862 he graduated as M. A. with first-class honors, and the gold medal in the department of Logic, Philosophy, and Political Economy. Two years later he was elected Fellow of University College.
In 1863 he published his first important work on economical science, entitled "A Serious Fall in the Value of Gold ascertained, and its Social Effects set forth." He consented to take the position of tutor in Owens College in 1863, and in 1866 was elected to the chair of Logic and Political Economy in that institution. The year ​previous he had read to the British Association a paper containing the fundamental positions of his later work, "Theory of Political Economy." In 1865 appeared the treatise "On the Coal Question," dealing with the problem of the exhaustion of the English coal-mines, the calculations of which were adopted by Mr. Gladstone and Mr. Mill in their treatment of the subject. In 1869 appeared the small work, "Substitution of Similars the True Principle of Reasoning;" in 1870 he read a paper before the Royal Society "On the Mechanical Performance of Logical Inference;" and about this time he completed his well-known Logical Machine. In 1870 appeared the first edition of the "Elementary Lessons in Logic." The "Theory of Political Economy" was published in 1871; and the author's great work, "The Principles of Science," was issued in two volumes in 1874.
"The Principles of Science" is a comprehensive treatise on pure and applied logic, or on the formal theory of inference and the methods of scientific investigation. The first book resumes the author's previous researches in pure logic, and carries them a step further. All inference is regarded as essentially reasoning from similars to similars, affirming that what is true of one thing is true of its like. The rules of inference flowing from this general principle, and the symbolical notation employed to express all the forms of thought, are stated and exemplified with great fullness. The particular novelty introduced is the view of induction, which Prof. Jevons regards as merely the inverse process of deduction. Thus, in deduction, we have given to us certain relations among terms or notions, and by the application of the formal laws of thought we develop all the possible combinations which are consistent with given relations. In induction, on the other hand, the combinations of terms are given, and we require to reason backward to the possible relations from which they may result. Insisting strongly upon his view of inductive inference. Prof. Jevons is led to criticise and reject the ordinary accounts of the process. He declines to admit that inductive research necessarily involves the idea of causation, and assimilates it more nearly to the mathematical doctrine of probability. The chapter in which he expounds the philosophy of inductive inference is peculiarly valuable, and deserves more careful criticism than it has yet received. As final result we have the complete subordination of induction to deduction; all inductive research, according to Prof. Jevons, consisting of three steps—framing an hypothesis as to the general law, deductively inferring results from it, and comparing the inferred conclusions with real fact.
The subordinate points involved in this theory of induction, such as the principles of combination and the general method of calculating probabilities, are treated very elaborately. The problem of inverse probability, which is, in Prof. Jevons's view, identical with the problem of induction, receives most careful attention. Some attempts have recently been made to carry out one or two of the elaborate ​logical computations shown to be necessary for the complete solution of the problem.
The remainder of the treatise is an exhaustive account of the methods of scientific investigation. What is most remarkable in this portion of the work is the combination of extensive and accurate knowledge of facts with perfect command of the most general principles. As a writer on scientific method, Prof. Jevons is fairly entitled to the credit of being a peer of predecessors so eminent as Herschel, Whewell, and Mill. He has given the fullest and best exposition of the methods actually employed by the greatest scientific workers, and has collected from all quarters a mass of most richly varied illustration.
The concluding book of the treatise is a brief but pregnant essay on the results and limits of scientific method. The outcome of the author's careful analysis of induction, the essentially probable character of what are called natural laws, is applied as a corrective to the rash scientific generalizations indulged in by many writers, and to the equally rash deductions from them. At the present time his. weighty remarks on the supposed contradiction between natural law and divine providence in any form are peculiarly deserving of attention.
Prof. Jevons published a volume, in 1875, entitled "Money, and the Mechanism of Exchange," forming part of "The International Scientific Series." It contains a lucid and admirably-written exposition of the nature and functions of money, the principles of circulation, the various forms of credit documents, and the elaborate mechanism (banks, check, and clearing systems) by which money exchanges are facilitated. Careful and complete historical notices are also given with regard to the various metallic currencies, modes of coinage, and regulations of issue, while technical matters, such as the qualities requisite for good metallic currency, the loss of weight in coins by usage, and the cost of keeping up the currency, receive due attention. His last publication was the little compendium of logic called "The Logic Primer," intended to give general readers some idea of this science.
In 1868 Prof. Jevons was appointed an Examiner in Political Economy in London University. In 1870 he was President of the Economic Section (Section E) of the British Association at its Liverpool meeting. In 1872 he was elected a Fellow of the Royal Society. In 1874 and 1875 he was an Examiner for the Moral Sciences Tripos at Cambridge. In the year 1876 the Senatus Academicus of Edinburgh University conferred upon him the honorary degree of LL. D.; and in the same year he was appointed Examiner in Logic and Moral Philosophy in London University. In March, 1876, Prof. Jevons announced his resignation of his professorship at Owens College; and in October, 1876, he entered upon the duties of the distinguished position to which he had been chosen, and which he now occupies, as Professor of Political Economy in University College, London.