"Some Problems of Logical Method in Political Economy"
1. In my analysis of the various logical methods I adhere in general to the treatises of Sigwart, Laurie, Bradley, Venn, and Mellone. I may have departed in some instances from the conventional treatment of the problems, especially in questions of interpretation, and I do not wish to attribute the responsibility for any of the logical doctrines here stated to any particular writers, unless I make specific reference to them.
2. Cf., e.g., Bertrand Russell, Principles of Mathematics, I, 11: "What is called induction appears to me to be either disguised deduction or a mere method of making plausible guesses." Cf. also E. B. Holt, The Concept of Consciousness, p. 12, for a similar opinion.
8. Senior, Political Economy; Cairnes, Character and Logical Method of Political Economy; J. S. Mill, System of Logic and Essays on Some Unsettled Questions of Political Economy; Jevons, Pure Logic and Principles of Political Economy. These form an extreme group in their condemnation of the inductive method. Sidgwick, Principles of Political Economy and Scope and Method of Political Economy (in collected Essays); Keynes, Scope and Method of Political Economy; and Bagehot, Economic Studies and Postulates of Political Economy (unfinished), are more moderate, but make induction subordinate.
9. "Induction is that operation of the mind by which we infer that what we know to be true in a particular case or cases will be true in all cases which resemble the former in certain assignable respects. In other words, Induction is the process by which we conclude that what is true of certain individuals of a class is true of the whole class" (System of Logic [7th ed.], I, 319).
10. In his description of the methods of induction Mill speaks only of the mechanical means of discovery of correlationships and ignores entirely the further problems of hypothesis and of intuitive discovery of the necessity of such correlationships as are found in each instance of their occurrence. As has been aptly remarked, Mill "ignores the constitutive faculty of the mind" (E. H. Blunt, article on "Logic," Encyclopaedia Britannica).
16. Mill seems to have succeeded in keeping this rather heroic assumption implicit, only because of his prepossession with the psychological aspects of economic data. Some of his followers were pried apart from this attitude by the criticisms of the historical school. Cf., e.g., Bagehot, Economic Studies, p. 19, and Ingram, History of Political Economy, p. 223, for a discussion of Bagehot's defection.
17. It was the tendency of the English school to reason from hypothetical premises, rather than their use of the deductive method, which was objected to by the "historical school." The "historical school" did not expect much from the use of the inductive method, but demanded that deductions, if they were made at all, should be made from categorical premises obtained from historical material.
18. Several attempts have been made to formulate the fundamental postulates from which all economic knowledge was to be derived, and they have been reduced to as few as two. Four seems to be the favorite number, however; cf. Senior, Political Economy, p. 26; Cairnes, Logical Method, p. 56; Cossa, Political Economy, p. 74; and for a discussion of these formulations, Sidgwick, Principles, p. 35 (2d ed.), and Keynes, Scope and Method, p. 243.
20. For a criticism, by an a priori economist, of the view that the study of disturbing causes does not come within the bounds of economic inquiry, see Cossa, Political Economy, (London, 1893) p. 78. Cossa also differs from Mill in contending that the "perturbing causes" can be most effectively investigated by induction, and thus grants to induction the important task of relating the hypotheses of the abstract political economy to the actual facts, as learned by inductive examination.
24. Principles of Political Economy, passim. Cf. Sidgwick, Principles of Political Economy, p. 32: "Why then, does Mill say that Political Economy is essentially an abstract science?... The only answer I can give is that in this and similar passages Mill is thinking, not of the theory of Production as he himself conceives and expounds it, but of the theory of Distribution and Exchange; and primarily of that portion of this latter subject which he distinguishes as 'statical' and not 'dynamical.' "
28. "There is not a clerk nor bookkeeper in the country who is not engaged in recording numerical facts for the economist.... It is chiefly a want of method and completeness in this vast mass of information which prevents our employing it in the scientific investigation of the natural laws of Economics."—(Jevons, Theory of Political Economy, p. 10). Note the inconsistency of this reasoning with Jevons' rejection of the inductive method in political economy. See Venn, Empirical Logic, p. 437, for a reference to Mill's inadequate treatment of the quantitative methods.
30. Mill elsewhere retracts his admission that some of the causes can be measured inductively, and asserts that the method really resolves itself into a series of deductions to discover the effects of a number of causes, in order to infer the effect of the remaining cause. He contends that a direct deduction applied to the cause whose importance we wish to gauge would give us more certain results and would give them sooner.
"Applied to social phenomena the Method of Residues presupposes that the causes from which part of the effect proceeded are already known, and as we have shown that these cannot have been known by specific experience, they must have been learned by deduction from principles of human nature; experience being called in only as a supplementary resource, to determine the causes which produced an unexplained residue. But if the principles of human nature may be had recourse to for the establishment of some political truths, they may for all"—(System of Logic, II, 461).
Wrapped up in this reasoning are two further doctrines: first, that even the "disturbing causes" all arise from "principles of human nature," or are psychological in character; and second, that even in the measurement of disturbing causes, or what Mill calls the "application" of political economy, induction is not an available method.
31. Cf. Jevons, Principles of Science, pp. 340-46, for a discussion of these methods of correction of results as applied to the method of difference—of which, of course, the method of concomitant variations is a special form.