SECOND DISSERTATION. _ 93 sical world, and the curtain was drawn aside which had so long concealed the great expe riment, by which nature herself manifests, at every instant, the inertia of body, and the composition of forces. To reconcile the real motion of the earth with its appearance of rest, and with our feeling of its immobility, required such an examination of the nature of motion, as discovered, if not its essence, at least its most general and fundamental proper ties. The whole science of rational mechanics profited, therefore, essentially by the disco very of the earth's motion.
A great barrier to philosophic improvement had arisen from the separation so early made, and so strenuously supported in the ancient systems, between terrestrial and celes tial substances, and between the laws which regulate motion on the earth, and in the hea vens. This barrier was now entirely removed ; the earth was elevated to the rank of a planet ; the planets were reduced to the condition of earths, and by this mutual approach, the same rules of interpretation became applicable to the phenomena of both. Principles derived from experiniants on the earth, became guides for the analysis of the heavens, and men were now in a situation to undertake investigations, which the most hardy adventurer in science could not before have dared to imagine. Philosophers had ascended to the knowledge of the affinities which pervade all nature, and which mark so strongly both the wisdom and unity of its author. • The light thus struck out darted its rays into regions the.most remote from physical in quiry. When men saw opinions entirely disproved, which were sanctioned by all anti quity, and by the authority of the greatest names, they began to have different notions of the rules of evidence, of the principles of philosophic inquiry, and of the nature of the mind itself. It appeared that science was destined to be continually progressive ; provid
ed it was taken for an inviolable maxim, that all opinion must be .ultimately amenable to experience and observation.
It was no slight addition to all these advantages, that, in consequence of the discus sions from which Galileo had unhappily been so great a sufferer, the line was at length . definitely drawn which was to separate the provinces of faith and philosophy from one another. It became a principle, recognised on all hands, that revelation, not being in tended to inform men of those things which the unassisted powers of their own under standing would in time be able to discover, had, in speaking of such matters, employed the language and adopted the opinions of the times ; and thus the magic circle by which the priest had endeavoured to circumscribe the inquiries of the philosopher entirely dis appeared. The reformatitin in religion which was taking plce about the same time, such energy to the human mind, contributed to render this emancipation more complete, and to reduce the exorbitant pretensions of the Romish church. The prohi bition against believing in the true system of the world either ceased altogether, or was reduced to an empty form, by which the affectation of infallibility still preserves the me mory of its errors. '