Detailed illustrations of the law would interest in proportion to the range of the investigation; and gratification and delight would keep pace with the deepening conviction of its universality; but the limits of an essay restrain the discussion to mere hints and suggestions, and general statements of principles which reflection must unfold into formal demonstration for every one in his own department of observation. Some inaccuracies of statement have been indulged to avoid the complexity which greater precision would have induced. Broad, frank thinking will easily bring up this looseness of language to the required closeness of thought as the advancing and deepening inquiry demands. Moreover, it may be difficult or impossible to meet every fact that presents itself with an instant correspondence in the alleged law; but such things cannot be avoided until people learn how to learn, and cease to meet novel propositions with a piddling criticism, or a wrangling spirit of controversy. Looking largely and deeply into facts in a hundred departments of observation will show the rule clear in the focal light of their concurrent proofs, or, looking out from the central position of _a priori_ reasoning, it will be seen in every direction to be a _necessary_ truth. It would be curious, and more than curious, to trace ascent of form up through ascertained gradation of quality in minerals, plants, fruits, and animal structures; and it would be as curious to apply a criticism derived from this doctrine to the purpose of fixing the rank and relations of all natural beings—in other words, to construct a science of taste and beauty, and, striking still deeper, a science of universal physiognomy, useful at once as a law of classification, and as an instrument of discovery. The scale would range most probably from the globular, as the sign of the lowest character, through the regularly graded movement of departure which in nature fills up all the stages of ascending function from a drop of fluid to the model configuration of, perhaps, that cerebral organ which manifests the highest faculty of the soul.