I can exchange the middle “diamond” for “anthracite.” As an external mark by which we can recognise at once the figure of a syllogism the middle is certainly very useful. But as the fundamental characteristic of a thing which is to be explained, we must take what is essential to it; and what is essential here is, whether we place two propositions together in order to compare their predicates or their subjects, or the predicate of the one and the subject of the other. Therefore, in order as premisses to yield a conclusion, two judgments must have a conception in common; further, they must not both be negative, nor both particular; and lastly, in the case in which the conceptions to be compared are the subjects of both, they must not both be affirmative. The voltaic pile may be regarded as a sensible image of the syllogism. Its point of indifference, at the centre, represents the middle, which holds together the two premisses, and by virtue of which they have the power of yielding a conclusion. The two different conceptions, on the other hand, which are really what is to be compared, are represented by the two opposite poles of the pile. Only because these are brought together by means of their two conducting wires, which represent the copulas of the two judgments, is the spark emitted upon their contact—the new light of the conclusion. Chapter XI.(22) On Rhetoric. Eloquence is the faculty of awakening in others our view of a thing, or our opinion about it, of kindling in them our feeling concerning it, and thus putting them in sympathy with us. And all this by conducting the stream of our thought into their minds, through the medium of words, with such force as to carry their thought from the direction it has already taken, and sweep it along with ours in its course. The more their previous course of thought differs from ours, the greater is this achievement. From this it is easily understood how personal conviction and passion make a man eloquent; and in general, eloquence is more the gift of nature than the work of art; yet here, also, art will support nature.