Lord Kames himself discussed like subjects in his " Elements of Criticism." The elegant preacher Dr.Hugh Blair lectured on the subject in the university of Edinburgh, and his "Lectures on Rhetoric and Belles-lettres " is one of the most useful books ever published on the art of composition.These works were used for several ages, not only in Scotland, but even in England, and helped to make rhetoric a leading branch of study in all the American colleges.Among all the works, Campbell's " Philosophy of Rhetoric " is perhaps the most philosophical, or is, at least, the one in which there is the most frequent discussion of philosophic problems.
He opens: " In speaking, there is always some end in view, or some effect which the speaker intends to produce on the hearer." The word <eloquence>, in its greatest latitude, denotes that art or talent by which the discourse is adapted to its end.In speaking of oratory suited to light and trivial matters, he endeavors to define wit."It is the design of wit to excite in {242} the mind an agreeable surprise, and that arising not from any thing marvellous in the subject, but solely from the imagery she employs, or the strange assemblage of related ideas presented to the mind."This end is effected in one or other of these three was, --first, in debasing things pompous or seemingly grave;""secondly, in agarandizing things, little and frivolous;thirdly, in setting ordinary objects by means not only remote, but apparently contrary, in a particular and uncommon point of view."He enlarges, as most of the Scottish metaphysicians have done, on the different kinds of evidence.He begins with intuitive evidence, which, he says, is of different sorts." One is that which results purely from intellection.
Of this kind is the evidence of these propositions: 'One and four make five;' things equal to the same thing are equal to one another; `the whole is greater than a part;' and, in brief, all in arithmetic and geometry.These are in effect but so many different expositions of our own general notions taken in different views." " But when the thing, though in effect coinciding, is considered under a different aspect, -- when what is single in the subject's divided in the predicate, and conversely, or when what is a whole in the one is regarded as a part of something in the other, -- such propositions lead to the discovery of innumerable and apparently remote relations." Under this head be also places, secondly, consciousness, "whence every man derives the perfect assurance which he hath of his own existence."He mentions, thirdly, common sense, giving to Buffier the credit of first noticing this principle as one of the genuine springs of our knowledge, whereas Shaftesbury had previously given it a special and important place.That he has not a definite idea of what common sense is as a philosophic principle, is evident from his stating that "in different persons it prevails in different degrees of strength," thus confounding the common principles of intelligence in all men with the sound sense possessed only by certain persons.He mentions a number of such principles, such as "whatever has a beginning has a cause;" "when there is in the effect a manifest adjustment of the several parts to a certain end, there is intelligence," "the course of nature will be the same tomorrow that it is to-day." He tries to draw distinctions between different kinds of intuitive truth.Thus, {243} in regard to primary truths of the third class, " it may be urged that it cannot be affirmed of them all at least, as it may be of the axioms in mathematics, or the assurances we have from consciousness, that the denial of them implies a contradiction." It is necessary, I believe, to draw some such distinctions as these between the various kinds of first truths; some of them seem to me to be of the nature of primitive cognitions, others of primitive judgments.But it is doubtful whether Campbell has been able to enunciate the nature of the difference.That he has no clear ideas of the relation of our primary perceptions to realities is evident from his statement."All the axioms in mathematics are but the enunciations of certain properties in our abstract notions, distinctly perceived by the mind, but have no relation to any thing without themselves, and cannot be made the foundation of any conclusion concerning actual existence; "as if the demonstrations of Archimedes as to conic sections had not been found to apply to the elliptic orbits of the comets as discovered by Kepler.
