substitute for identity, as a basis of Deduction or Inference; and for our purpose of illustrating similarity, the striking out of analogies is very much in point. As an example of analogical reasoning or inference, I may take the comparison of human society to a family, with the transfer of the duties and powers of the head of the family to the sovereign of the state; this transfer is an inference or deduction, and is often tendered as a reason for the tutelary and despotical character of the sovereign. The two cases are not identical; they have an analogy, and a good reasoner remarks how far the analogy holds, and confines his inferences within those limits. In like manner, human society has suggested the analogy of herds and hives, an analogy much insisted on by Aristotle. A mind well stored with numerous conceptions, the fruit of various studies, and having at the same time a good reach of the identifying faculty, can strike out analogies when identities fail; and by means of these a certain amount of insight is sometimes obtainable. We have had occasion to advert to one remarkable scientific analogy, namely, that between nerve force and common electricity, from which we have not hesitated to draw inferences in order to support the view taken of the manner of working of the nervous system. Sometimes a farther investigation will convert an analogy into an identity, as was the case with gravitation, if it be true that Hooke went so far as to quote terrestrial gravity as an illustration of solar attraction. But analogies in the proper sense of the word are similarities of relation in diversity of subject, as in the case of society above quoted, where the analogical character is the permanent fact. The circumstance of evolution attaching to the vegetable and animal kingdoms, the successive stages of birth, growth and decay, is but an analogy as between a plant and an animal; to a still greater degree is this the case when we are comparing the mental development of a human being with the growth of a tree, not to speak of the much more remote comparison between the growth of humanity, as a whole, and the progress of an individual plant, or animal. This last analogy is, indeed, too faint to be of any value, and

MECHANICAL INVENTIONS.

525

is misleading if deductions are made from it. The logical caution that must accompany discoveries of supposed identity is still more requisite in the slippery regions of analogy.

BUSINESS AND PRACTICE.

38. In Business and Industry, in the power of intelligence applied to the affairs of life, in practical genius, we find exemplified the discovery of deep identities amid superficial differences. In the inventions of practical art, no less than in the discoveries of science, the identifying faculty is called into play.

The labours of Watt, in the steam engine, might with great propriety be cited, to correspond with the greatest strokes of scientific identification. Perhaps his 'governor balls' is the most illustrative example for our present purpose. Here he had to hit upon a method of opening and closing a valve, in connexion with the diminution or increase of the speed of a very rapid wheel movement; and no device in the range of existing machinery would answer this object. He had therefore to venture out into the region of mechanical possibility, to seek among mechanical laws in general, or among very remote natural phenomena, for a parallel situation; and he found the only case that has yet been hit upon, namely, the action of a centrifugal force, where two revolving bodies separate, or come together, according as the rate of revolution is accelerated or retarded. I am not aware of any stroke of remote identification in the history of mechanical invention, surpassing this in intellectual reach; if such a power of bringing together the like out of the unlike were of usual occurrence, the progress of discovery would be incalculably more rapid. Another instance of Watt's power of identifying a practical situation with some other case where the requisite construction is given, was the suggestion of a lobster-jointed pipe, for conveying water across the bottom of the river Clyde, and which answered perfectly. The inventive genius is ever ready with a suggestion derived from some

already existing device disguised by considerable disparity, either in the arrangements of nature or in the constructions of art. Identifying power, although not expressing everything that constitutes an inventor, will always be found a prominent feature in the character. As in all other departments, the identifying power must ply its energy in the proper region, and this is determined by the nature of the previous acquisitions, and the attraction of the mind for the specific class of objects wherein the invention shows itself.

An isolated discovery may prove but little as to the intellect of the discoverer, but a career of invention implies a large reach of the identifying faculty. The fertility of new suggestions displayed by some minds is a distinction founded on the power of piercing through disguises and bringing past and present together through an energetic force of reinstatement. Great inventors in all regions of practice,-whether in mechanical industry, government, laws, military affairs, medicine, education, could be proved to abound in these strokes of similarity; and it would be seen that whatever other circumstances might contribute to their sagacity, this is the most indispensable.

39. In the able administration of private business and public affairs, we shall be able to detect the same force at work, although it may not in this case be called invention or genius. Either in meeting new cases, or in bringing superior methods to bear upon old, there is a march of mind, an advance over routine, which marks the able administrator; and here too the link of power consists in a more than ordinary force of identification. When a present emergency is exactly like a previous one, it recals that one without difficulty, and is treated as that was treated; when it corresponds exactly to no one previous, a subtler mind is wanted; a parallel must be sought for away from the routine of cases. Into quite remote regions of affairs the man of penetration is carried, and finds something in point where perhaps no parallel was ever drawn before. The application of the Syllogism to Law pleadings was a great legal improvement, which has persisted while scholastic forms have gone generally into decay. No routine

TRANSFER OF PRACTICAL DEVICES.

527

lawyer was capable of such an innovation. If for illustration's sake we suppose it to have been the work of one person, it implies a mind that came to the study of law previously prepared with the scholastic training, and detecting in the pleadings before the courts a real identity in form with the discussions of the schools, although hitherto conducted with no such method or precision. The transference of the syllogism to the legal reasonings would be the consequence of this feeling of identity; and hence would arise that capital requirement of making parties plead to the law and to the facts of the case separately, instead of huddling up both in one argument as is usually done in the controversies of every-day life. An innovation of this nature would be not unlikely to be introduced when cases arose of more than usual perplexity, such as make manifest the inadequacy of existing methods.

It is a usual circumstance for practical devices to be first hit upon in obvious cases, and thence transferred to other cases of a like nature but of more complexity. Thus in the great institution of the Division of Labour now so widely ramified over all departments of industry, a progressive application could be traced; we should find it commencing in manual industry, in the separation of the primitive classes of agriculturist, artisan, trader, soldier, and priest, and, in later times especially, extended into the large manufactory, into public business, and scientific research. In every new step there would arise in the mind of some one person or other a feeling of similarity between the exigencies of a business in hand and the cases where the method of divided labour was already in operation, and this identification would suggest the further extension of the practice. I do not at present speak of the faculty required for overcoming the difficulties of detail in all new applications of old machinery, (although here too it would be found that a fertile power of recalling identities in diversity would be the principal instrument of success in so far as the intellect was concerned,) I confine myself to the broad suggestion of a device through derivation from some existing parallel case.

In the progress of free governments there has been gradually diffused from the lower to the higher and more difficult posts the principle of responsibility as a check upon the abuse of power. This practice grew up by a process of extension, until in the constitutional governments of Great Britain and the United States it came to include every executive officer in all departments of state. The experience had of the practice in the more humble functionaries suggested its application to the exactly parallel case of superior officers, and after much struggle, not of an intellectual kind, it got to be introduced into modern free communities, as it had been in the constitution of ancient Athens.

The principle of non-interference with individual tastes and sentiments, except in so far as these affect the legitimate happiness of others, is recognised in certain cases, and has had a tendency to expand itself by assimilation into cases encumbered with obstructive circumstances. Hence has sprung up what amount of toleration in belief and conduct we now enjoy; but the difficulty in proceeding far with this extension shows how powerfully such sentiments as the love of domination and of uniformity may stifle the assimilating action of the intellect.

In the suggestions of a practical mind, the identification must always turn upon the relevant circumstances, and overcome other attractions of sameness on irrelevant points. To attain to this characteristic is the end of a practical education, which makes the person familiar with the aspects that serve the ends contemplated. Thus a lawyer in recovering from his past experience the precedents and analogies suitable to a case in hand is impelled by the force of similarity working in his mind; but, of the many peculiarities of the case, he excludes the assimilating action of all except the one that would govern its decision before a judge. His education must serve him in making this discrimination; and if (as will happen) he is by natural temperament keenly alive to this one feature that constitutes legal relevancy, and indifferent to all other points of interest in the case, he is a born lawyer, just as Newton with his natural avidity for mathematical