What is this method? Whichever of these sciences we examine, we find the course uniformly pursued to be that of setting out with propositions of which the negations are inconceivable, and advancing by successive dependent propositions, each of which has the like character—that its negation is inconceivable. In a developed consciousness (and of course I exclude minds of which the faculties are unformed) it is impossible to represent things that are equal to the same thing as being themselves unequal; and in a developed consciousness, action and re-action cannot be thought of as other than equal and opposite. In like manner, every _because_ and every _therefore_, used in a mathematical argument, connotes a proposition of which the terms are absolutely coherent in the mode alleged: the proof being that an attempt to bring together in consciousness the terms of the opposite proposition is futile. And this method of testing, alike the fundamental propositions and all members of the fabrics of propositions raised upon them, is consistently pursued in verifying the conclusion. Inference and observation are compared; and when they agree, it is held inconceivable that the inference is other than true. In contrast to the method which I have just described, distinguishable as the legitimate _a priori_ method, there is one which may be called—I was about to say, the illegitimate _a priori_ method. But the word is not strong enough; it must be called the inverted _a priori_ method. Instead of setting out with a proposition of which the negation is inconceivable, it sets out with a proposition of which the affirmation is inconceivable, and therefrom proceeds to draw conclusions. It is not consistent, however: it does not continue to do that which it does at first. Having posited an inconceivable proposition to begin with, it does not {201} frame its argument out of a series of inconceivable propositions. All steps after the first are of the kind ordinarily accepted as valid. The successive _therefores_ and _becauses_ have the usual connotations. The peculiarity lies in this, that in every proposition save the first, the reader is expected to admit the logical necessity of an inference drawn, for the reason that the opposite is not thinkable; but he is not supposed to expect a like conformity to logical necessity in the primary proposition. The dictum of a logical consciousness which must be recognized as valid in every subsequent step, must be ignored in the first step. We pass now to an illustration of this method which here concerns us. The first sentence in Kant’s first chapter runs thus:—“Nothing can possibly be conceived in the world, or even out of it, which can be called good without qualification, except a Good Will.”[23] And then on the next page we come upon the following definition:―