And now I come to a further peculiarity of this natural and spontaneous ratiocination. This faculty, as it is actually found in us, proceeding from concrete to concrete, belongs to a definite subject-matter, according to the individual. In spite of Aristotle, I will not allow that genuine reasoning is an instrumental art; and in spite of Dr. Johnson, I will assert that genius, as far as it is manifested in ratiocination, is not equal to all undertakings, but has its own peculiar subject-matter, and is circumscribed in its range. No one would for a moment expect that because Newton and Napoleon both had a genius for ratiocination, that, in consequence, Napoleon could have generalized the principle of gravitation, or Newton have seen how to concentrate a hundred thousand men at Austerlitz. The ratiocinative faculty, then, as found in individuals, is not a general instrument of knowledge, but has its province, or is what may be called departmental. It is not so much one faculty, as a collection of similar or analogous faculties under one name, there being really as many faculties as there are distinct subject-matters, though in the same person some of them may, if it so happen, be united,—nay, though some men have a sort of literary power in arguing in all subject-matters, _de omni scibili_, a power extensive, but not deep or real. This surely is the conclusion, to which we are brought by our ordinary experience of men. It is almost proverbial that a hard-headed mathematician may have no head at all for what is called historical evidence. Successful experimentalists need not have talent for legal research or pleading. A shrewd man of business may be a bad arguer in philosophical questions. Able statesmen and politicians have been before now eccentric or superstitious in their religious views. It is notorious how ridiculous a clever man may make himself, who ventures to argue with professed theologians, critics, or geologists, though without positive defects in knowledge of his subject. Priestley, great in electricity and chemistry, was but a poor ecclesiastical historian. The Author of the Minute Philosopher is also the Author of the Analyst. Newton wrote not only his “Principia,” but his comments on the Apocalypse; Cromwell, whose actions savoured of the boldest logic, was a confused speaker. In these, and various similar instances, the defect lay, not so much in an ignorance of facts, as in an inability to handle those facts suitably; in feeble or perverse modes of abstraction, observation, comparison, analysis, inference, which nothing could have obviated, but that which was wanting,—a specific talent, and a ready exercise of it.