Such is ratiocination, in what may be called a state of nature, as it is found in the uneducated,—nay, in all men, in its ordinary exercise; nor is there any antecedent ground for determining that it will not be as correct in its informations as it is instinctive, as trustworthy as are sensible perception and memory, though its informations are not so immediate and have a wider range. By means of sense we gain knowledge directly; by means of reasoning we gain it indirectly, that is, by virtue of a previous knowledge. And if we may justly regard the universe, according to the meaning of the word, as one whole, we may also believe justly that to know one part of it is necessarily to know much more than that one part. This thought leads us to a further view of ratiocination. The proverb says, “Ex pede Herculem;” and we have actual experience how the practised zoologist can build up some intricate organization from the sight of its smallest bone, evoking the whole as if it were a remembrance; how, again, a philosophical antiquarian, by means of an inscription, interprets the mythical traditions of former ages, and makes the past live; and how a Columbus is led, from considerations which are common property, and fortuitous phenomena which are successively brought to his notice, to have such faith in a western world, as willingly to commit himself to the terrors of a mysterious ocean in order to arrive at it. That which the mind is able thus variously to bring together into unity, must have some real intrinsic connexion of part with part. But if this _summa rerum_ is thus one whole, it must be constructed on definite principles and laws, the knowledge of which will enlarge our capacity of reasoning about it in particulars;—thus we are led on to aim at determining on a large scale and on system, what even gifted or practised intellects are only able by their own personal vigour to reach piece-meal and fitfully, that is, at substituting scientific methods, such as all may use, for the action of individual genius.