It is a wonderful property of the human mind, that when once a momentum has been given to it in a fresh direction, it pursues the new path with obstinate perseverance, in all conceivable bearings, to its utmost extremes. And by the startling consequences which arise out of these extremes, it is first awakened to its error, and either recalled to some former track, or receives some fresh impulse, which it follows with the same eagerness, and admits to the same monopoly. Thus in the 13th century the first science which roused the intellects of men from the torpor of barbarism, was, as in all countries ever has been, and ever must be the case, the science of _Metaphysics_ and _Ontology_. We first seek what can be found at home, and what wonder if truths, that appeared to reveal the secret depths of our own souls, should take possession of the whole mind, and all truths appear trivial which could not either be evolved out of similar principles, by the same process, or at least brought under the same forms of thought, by perceived or imagined analogies? And so it was. For more than a century men continued to invoke the oracle of their own spirits, not only concerning its own forms and modes of being, but likewise concerning the laws of external nature. All attempts at philosophical explication were commenced by a mere effort of the understanding, as the power of abstraction; or by the imagination, transferring its own experiences to every object presented from without. By the former, a class of phenomena were in the first place abstracted, and fixed in some general term: of course this could designate only the impressions made by the outward objects, and so far, therefore, having been thus metamorphosed, they were effects of these objects; but then made to supply the place of their own causes, under the name of occult qualities. Thus the properties peculiar to gold, were abstracted from those it possessed in common with other bodies, and then generalized in the term _Aureity_: and the inquirer was instructed that the Essence of Gold, or the cause which constituted the peculiar modification of matter called gold, was the power of aureity. By the latter, _i.e._ by the imagination, thought and will were superadded to the occult quality, and every form of nature had its appropriate Spirit, to be controlled or conciliated by an appropriate ceremonial. This was entitled its SUBSTANTIAL FORM. Thus, physic became a sort of dull poetry, and the art of medicine (for physiology could scarcely be said to exist) was a system of magic, blended with traditional empiricism. Thus the forms of thought proceeded to act in their own emptiness, with no attempt to fill or substantiate them by the information of the senses, and all the branches of science formed so many sections of logic and metaphysics. And so it continued, even to the time that the Reformation sounded the second trumpet, and the authority of the schools sank with that of the hierarchy, under the intellectual courage and activity which this great revolution had inspired. Power, once awakened, cannot rest in one object. All the sciences partook of the new influences. The world of experimental philosophy was soon mapped out for posterity by the comprehensive and enterprising genius of Bacon, and the laws explained by which experiment could be dignified into experience.(2) But no sooner was the impulse given, than the same propensity was made manifest of looking at all things in the one point of view which chanced to be of predominant attraction. Our Gilbert, a man of genuine philosophical genius, had no sooner multiplied the facts of magnetism, and extended our knowledge concerning the property of magnetic bodies, but all things in heaven, and earth, and in the waters beneath the earth, were resolved into magnetic influences.