ing is unsound. In all these respects I endeavoured to show that the character of an economic law is strictly analogous to that of those laws of physical nature which are obtained, or which may be obtained, by deduction from the ultimate principles of the sciences to which they belong.

So far, then, the analogy between a 'law' as understood in Political Economy and a 'law' as understood in the more advanced physical sciences holds good.

In the present lecture I propose to call your attention to a circumstance in which this analogy fails, and to the consequences which result from this failure, in the development of economic truth. In both departments of speculation alike a law of nature expresses a tendency constantly influencing phenomena; but in the physical sciences the discovery of a law of nature is never considered complete till, in addition to the general tendency, an exact numerical expression is found for the degree of force with which the tendency in question operates.

It is the character," says Sir John Herschel,1 "of all the higher laws of nature to assume the form of precise quantitative statement. Thus the law of gravitation, the most universal truth at which human reason has yet arrived, expresses not merely the general fact of the mutual attraction of all matter; not merely the vague statement that the influence decreases as the distance increases, but the exact numerical rate at which that decrease takes place; so that, when its amount is known at any one distance, it may be calculated exactly for any other. Thus, too, the laws of crystallography, which limit the forms assumed by natural substances, when

1 Natural Philosophy,' p. 123.

left to their own inherent powers of aggregation, to precise geometrical figures with fixed angles and proportions, have the same essential character of strict mathematical expression, without which no exact particular conclusions could ever be drawn from them."

To give one example more, the use of the balance has brought chemistry into the category of those sciences the laws of which admit of quantitative statement. The chemist is consequently able, not merely to describe the general nature of the reaction which will take place between certain substances under known conditions, but can give beforehand a numerical statement of the exact proportions in which the several elements will unite in the resulting compound.

This is a degree of perfection, however, which it does not seem possible that Political Economy, any more than jurisprudence, philology, or any of those branches of speculation, which derive their premisses from the principles of human nature, should ever attain.' For, although the general character of these principles may be ascertained, and although when stated with sufficient precision they may be made the basis of important deductions, yet they do not, from the nature of the case, admit of being weighed and measured like the elements and forces of the material world: they are therefore not susceptible of arithmetical or mathematical expres

1 This remark might, perhaps, be extended to embrace the organic sciences in general. The laws of organic development, for example, expressing general tendencies, are never formulated in other than general terms. See 'Habit and Intelligence,' by J. J. Murphy, vol. i., pp. 201, 202, 212.

sion; and hence it happens that, in speculating on results which depend on the positive or relative strength of such principles, perfect precision, numerical accuracy, is not attainable. Political Economy seems on this account necessarily excluded from the domain of exact science.1

Mr. Macleod considers Monetary Science (which he appears to regard as commensurate or nearly so with Political Economy), as 'an exact science.' In the Introduction to his 'Theory and Practice of Banking,' vol. ii., p. 25, he writes as follows:-"These principles then act with unerring certainty-they are universally true- human instinct is as certain, invariable, and universal in its nature as the laws of motion

AND THAT IS THE CIRCUMSTANCE WHICH RAISES MONETARY SCIENCE TO

THE RANK OF AN EXACT OR INDUCTIVE SCIENCE. It is this which renders it possible to establish it upon as sure, solid, and unimperishable a basis as mechanical science. Alone of all the political sciences its phenomena may be expressed with the unerring certainty of the other laws of nature." (The capitals are the Author's.) Mr. Macleod seems to confound an exact' with a positive science. In order that a science be 'exact,' it is necessary, not only that its premisses be 'universal and invariable,' but further, that they be susceptible of precise quantitative statement. If Mr. Macleod can show that both these conditions are satisfied in the present instance,-that the character of 'human instinct' can be known, and also that its force can be measured, as the force of gravitation, he will then have established a basis for an exact science of Political Economy.

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Mr. Jennings, in his 'Natural Elements of Political Economy,' appears to take the same view. "Our instruments," he says, though acting on and through the principles of human nature, are found to consist of metallic indices [money] related as parts and multiples, and not less capable of being made subservient to the processes of exact calculation than are the instruments of any purely physical act. The results of these principles when observed may be expressed in figures; as may also the anticipated results of their future operation, or such relations as those of Quantity and Value, Value and Rate of Production may be exhibited in the formulæ and analyzed by the different methods of Algebra and of Fluxions."-pp. 259-260.

There is no doubt that economic results when they have happened may be expressed in figures; but I apprehend something more than this is requisite to render a science exact.' Mr. Jennings indeed. adds, 'as may also the anticipated results of their future operation ;'

This quality of economic doctrines will be made more clear by a few examples.

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but the question is, have we such data as will warrant us in accepting as trustworthy the results thus obtained? Will our calculations turn out, not merely generally, but 'exactly' true? Instead of dealing in general terms, let us take a specific case the determination of the price of corn-and consider what in this instance would be necessary in order to arrive at an exact' result. The following is taken from Tooke's History of Prices' :-" But, further, supposing that both the results of the harvests and the stock on hand were made known with sufficient approach to accuracy by Government returns, there would yet remain the greatest uncertainty in the corn markets unless the probable extent of the Supplies from abroad could be known. And, granting all these grounds for estimates of actual and forthcoming supplies to be within the power of Government to ascertain, there would be yet another influence on prices,—and consequently a cause of fluctuation,—namely, the speculative views operating on the minds of both buyers and sellers in the contemplation of circumstances likely to affect the produce of the next ensuing harvest. From the time of sowing to that of gathering the wheat crop, the casualties of the weather exercise an influence on the markets, and thus cause fluctuations at critical periods of the season. Among the claims put forth for agricultural statistics, it has been required, as a part of the information insisted upon, that there should be periodical Government returns of the appearance of the growing crops.

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These, and other contingencies more or less important, are causes of fluctuation from uncertainty of supply. But assuming, for mere argument sake, the statistics of supply to be perfect, there still remain the uncertainties of demand.

"For the reasons which I have before stated, the variations of consumption are on a much smaller scale than those of supply; but the demand on the markets may occasionally have a considerable temporary influence on prices, as in the case of the autumn of 1854, of the millers and bakers trying to get into stock, after having left themselves bare. There may likewise be a demand for Exportation to France or to other parts of the Continent. How could any information from Government have supplied the statistics of such a demand? But adopting the extreme and extravagant hypothesis, that all these elements of uncertainty admitted of having great light thrown upon them by statistics and other information published by Government, there would still remain to be solved the problem of what the price ought in consequence to be; and this, I will venture to say, will be found to be an insoluble problem."-Vol. v., pp. 88, 89.

In order that the problenis of Political Economy should be made sub

The decline of profits, as nations advance in wealth and numbers, is a circumstance which has long attracted the attention of economists. It has also been observed that, in the course of this progress, a minimum point is attained, beyond which profits do not further decline; and further, that this minimum is different in different nations. In China, it is stated that profits show no tendency to fall below 30 per cent. per annum ; while in England profits have fallen perhaps to 10 per cent., in Holland probably lower, and in other countries the decline has been arrested at other points. Now the point in the descent at which the fall is arrested—that is to say, the minimum rate of profit which can for any considerable time exist in any community-is determined by the strength of a principle which Mr. Mill has called the effective desire of accumulation.' This effective desire of accumulation' is a general expression to denote the degree in which the desire for wealth predominates over those principles of human nature which obstruct its operation-such as the love of ease, and the desire for immediate enjoyment. When a man employs his

servient to 'exact' treatment, it would be necessary, not only that 'the instruments, on and through which the principles of human nature [in the pursuit of wealth] act,' should be capable of quantitative measurement, but also that the principles themselves, as well as the conditions under which they come into operation, should be susceptible of exact numerical statement. The most perfect system of weights and measures would never have made chemistry an exact science, if the law of equivalent proportions had not been discovered.

Some forcible remarks in the same sense will be found in the Philosophie Positive, tome iv., pp. 512, 513. The attempt to employ mathematical formulæ in inquiries of the social order M. Comte regards as 'l'involontaire témoignage décisif d'une profonde impuissance philosophique.'