The slender reed through which Philosophy breathed her first musical whisperings is laid by, and the sacred lyre of Theology is silent or little heeded. But the mighty organ of Modern Science with its hundred stops, each answering to some voice of Nature, takes up the pausing strain, and as we listen we recognize through all its mingling harmonies the simple, sublime, eternal melody that came from the lips of Timaeus the Locrian! The same doctrine reappears in various forms: in the popular works of Derham and Paloy and the Bridgewater Treatises; in the learned and thoughtful pages of Burdach, and in the mystical rhapsodies of Oken. But never, we believe, was it before enforced and illustrated by so imperial a survey of the whole domain of Natural Science as in the volumes before us. We are not disposed to discuss at any length the opinion maintained by Mr. Agassiz, that life has not grown out of the necessary action of the physical laws. If we accept the customary definitions of the physical laws, we accede most cordially to his proposition. As opposed to the fancies of Epicurus and his poet, Lucretius, or to modern atheistic doctrines of similar character, we have no qualification or condition to suggest which might change its force or significance. When we remember that the genius of such a man as Laplace shared the farthest flight of star-eyed science only to "waft us back the tidings of despair," we are thankful that so profound a student of Nature as Mr. Agassiz has tracked the warm foot-prints of Divinity throughout all the vestiges of creation. There is danger, however, that, in accepting this doctrine as a truth, we may be led into an inexact conception of the so-called physical laws, unless we closely examine the sense in which we use the expression. The forces which act according to these laws, and the various forms of the so-called _matter_, or concrete forces, are often spoken of as if they were blind agencies and existences, acting by an inherent fate-like power of their own. But if everything outside of our consciousness resolves itself, in the last analysis, into force, or something capable of producing change, and if force existing by the will of an omniscient and omnipresent Being, to whom time has no absolute significance, is simply God himself in action, then we shall find it impossible to limit the causal agency of the physical forces. All we can say is, that commonly they appear to move in certain rectilinear paths, in which they manifest a degree of uniformity and precision so amazing that we are lost in the infinite intelligence they display,--unless we become perfectly stupid to it, and think, as in the old fable, there is no music in it because we are made deaf by its continued harmony. No single leaf ever made a mistake in falling, though in so doing it solved more problems than were ever held in all the libraries that have changed or are changing into dust or ashes.