must acquire, slowly and patiently, letter by letter, the alphabet in which nature writes her answers to such inquiries; the first students wished to divine, at a single glance, the whole import of the book." As their first inquiry, they endeavoured to discover the origin and principle of the universe. Thales maintained that it was water; according to another, it was air; while a third considered fire as the origin of all things. This last hypothesis, it may be remarked, has been revived by a popular cosmogonist of our own day, who has found the seminal principle of all things, including the various ranks of animate being, the body, and even the soul, of man, in a primitive fiery mist. These wide and ambitious doctrines, it has been well remarked, are "better suited to the dim magnificence of poetry than to the purpose of a philosophy which was to bear the sharp scrutiny of reason. When we speak of the principles of things, the term, even now, is very ambiguous and indefinite in its import; but how much more was that the case in the first attempts to use such abstractions !" The history of physical science, as it was studied by the schoolmen during the Middle Ages, is quite as unsatisfactory as the record of its treatment by the ancients. Logic, which I have ventured to class with the metaphysical sciences, because it is exclusively concerned with the relations of ideas, or with abstractions of the highest order, now claimed the chief attention in the schools. There were two reasons for giving it this preference : first, because it was held, as before, that all knowledge might be deduced from general ideas, so as to avoid the necessity of studying nature or observing particulars; and secondly, because it was believed that the ancients had already exhausted the inquiry and completed the work, so that all truth might be ascertained, and all controversies terminated, by a right interpretation of the works of Aristotle and his commentators,-this interpretation being governed, of course, by the rules of a sound logic. The scholastics. held, "that all science may be obtained by the use of reasoning alone, that by analyzing and combining the notions which common language brings before us we may learn all that we can know." The fallacy of this, it has been well remarked, con sists in mistaking the universality of the theory of language for the generalization of facts. All words, excepting proper names, denote either general conceptions or abstract ideas; and the study of the relations of words is therefore a study of the relations of ideas, and must proceed by the former of the two methods which we have been considering, - that is, by intuition. and demonstration. We might well expect that physical science, or the study of matters of fact, when pursued by this method, would produce only nugatory or profitless results. It has been stated on high authority, that not one step had really been taken in physical science down to the period of the Revival of Letters, not a foot of ground had been gained by the labors of more than two thousand years. This statement is perhaps too strong; for something was undoubtedly accomplished in astronomy by Hipparchus and Ptolemy, something in natural history by such observers as Aristotle, Theophrastus, and Pliny, while the medical profession, even at the present day, does not wholly repudiate the authority of Hippocrates and Galen. But how little real progress the human mind had made during this long lapse of centuries may be correctly inferred from the round of studies pursued at the universities; the course of seven sciences, included under the fantastic names of the trivium and the quadrivium, comprised grammar, logic, and rhetoric, together with arithmetic, geometry, music, and astronomy. Of these, only the last can be ranked among the physical sciences, as music was then only an art which had not been reduced to its scientific principles. The others are all metaphysical in character, and the only organon, or method of investigation, which was then in use, being appropriate to these, the success with which they were cultivated affords a striking contrast to the barrenness of physical inquiry. Logic came almost perfect from the hands of him who may be called its inventor. Sir William Hamilton, the most accomplished logician of our own day, asserts distinctly, that there has been, "in fact, no progress made in the general development of the syllogism since the time of Aristotle." The case of mathematics is nearly as strong, the geometry of Euclid and Archimedes being still the boast of the science. These were the results of applying the appropriate mode of reasoning to the metaphysical sciences, or those which are concerned exclusively with the relations of ideas; while the inappropriateness of this same mode of reasoning to physical science, that is, to matters of fact, is proved by the almost total failure of all attempts in this department for more than twenty centuries. It is not necessary to dwell here on so familiar a history as that of the sudden rise and extraordinary development of physical science at the close of the sixteenth century. The rapid succession of brilliant discoveries made by Galileo, Stevinus, and Gilbert, was in itself a proof that they had at length hit upon the true method of physical investigation, just before the illustrious Englishman-himself hardly capable of reducing any one of his own rules successfully to practice, but gifted with an intellect no less clear and penetrating than comprehensive and profound, and with a sagacity and hopefulness which unrolled before him the history of the future triumphs of science almost as distinctly as the record of its past defeats-supplied the rationale of this method, reduced it to a complete system, and evolved and stated with wonderful precision the rules for its successful use, in those immortal works which have gained for him the deserved title of Father of the Inductive Philosophy. To say that the inductive method was practised in some cases before the time of Bacon is about as idle as to assert that men sometimes reasoned correctly before Aristotle wrote his Logic; though the assertion in the former case is not true to the same extent as in the latter, since the latter half of the century in which Bacon was born, though not that in which his principal works were published, witnessed the first successful application of this method to physical science. The merit of these two great men is of the same order; each wrought out with scientific precision and completeness the logic of discovery and proof in one of the two great departments of human knowledge. The one taught us the theory of reasoning syllogistically, or to a demonstration, about the relations of ideas; the other showed us the theory of reasoning inductively from matters of fact. The extraordinary success of physical inquiry after Bacon's time tended naturally to the depression, and somewhat to the injury or corruption, of abstract science. The undue extension of the inductive method to the region of pure ideas produced the ethical system of Hobbes, himself a friend and disciple of the great master, but whose philosophy is now a byword from its degrading principles, and its tendencies to selfishness in morals, to materialism in philosophy, and to despotism in politics. Among his successors may be counted Mandeville, "the buffoon and sophister of the ale-house," and the English school of deists of the early part of the last century, including Bolingbroke, the friend and philosophical instructor of Pope. From him his satirical pupil learned to sneer at the metaphysicians of the older school, who, in the Universities or the Church, distrustful of the tendencies of modern physical science, and perhaps ignorant alike of its principles and its practice, still kept up their fondness for ancient and abstract learning. Prophesying the triumph of dulness and obscurity, the poet exclaims, "As Argus' eyes, by Hermes' wand oppressed, Thus, at her felt approach and secret might, Art after art goes out, and all is night. See skulking Truth to her old cavern fled, Physic of Metaphysic begs defence, And Metaphysic calls for aid to Sense : See Mystery to Mathematics fly; In vain; they gaze, turn giddy, rave, and die.” A later instance of the erroneous application of the method of physical inquiry to metaphysical subjects may be found in the writings of the celebrated David Hartley, who endeavoured to account for the course and association of our ideas by vibrations and vibratiuncles in the medullary substance of the brain. Of the same school was Dr. Priestley, whose just fame for his brilliant discoveries in natural science inclines one to speak tenderly of his philosophical speculations, though his habits, formed in the laboratory and other schools of experimental investigation, betrayed him into the avowed support of materialism, and of what he calls the doctrine of "philosophical necessity." The influence of the same cause of error may be traced in the works of the French philosophers, so called, of the last century, especially in those of Helvetius, Volney, D'Holbach, and Condillac. Helvetius, for instance, refusing to receive any other evidence than that of the senses, tracing all ideas to this source, and assuming the inductive method to be the only guide to knowledge, can find no cause for the superiority of man over the brute, except that the human hand is a more convenient instrument than the foot of a quadruped, which terminates in horn, nails, or claws. "The life of animals, in general," he observes, "being of a shorter duration than that of man, does not permit them to make so many observations, or to acquire so many ideas; and animals, being better armed and better clothed by nature than the human species, have fewer wants, and consequently fewer motives to stimulate or exercise their invention. Who can doubt, then," he triumphantly asks, "that if the wrist of a man had been terminated by the hoof of a horse, the species would still have been wandering in the forest?" Such vagaries of speculation are not a whit more respectable than the opposite errors of the schoolmen, who sought to interpret nature by the relations of abstract ideas, or, in other words, to ascertain facts by the aid of a transcendental logic. It would be very unjust to accuse the inductive method of leading to these gross blunders, which have arisen solely from a misapplication of that method, from an extension of it to a province which it was never formed to govern, namely, the region of pure mental conceptions. We shall be likely to avoid both causes of error by keeping constantly in view the axiom, that the methods as well as the objects of physical and of metaphysical inquiry are radically different. We never can demonstrate a matter of fact; we |