# Philosophical Works of the Late James Frederick Ferrier/Institutes of Metaphysic (1875)/Section 1/Proposition 18

The Institutes of Metaphysic, Philosophical Works of the Late James Frederick Ferrier (1875 ed., Vol. 1). (E. L. Lushington, & A. Grant, Eds.) Edinburgh: William Blackwood and Sons. pp. 363-366.
PROPOSITION XVIII.
THE RELATIVE IN COGNITION.
DEMONSTRATION.
The demonstration commences with the definition of the relative, which is nearly identical with that of the phenomenal. "The relative is whatever can be known or conceived only when a correlative is known or conceived along with it." But that which can be known or conceived only when a correlative is known or conceived along with it cannot be known or conceived by itself. Therefore there is no mere relative in cognition; in other words, the relative per se or by itself, is, of necessity, unknowable and unknown.
OBSERVATIONS AND EXPLANATIONS.
1. Although this and the three following propositions are mere repetitions of the four immediately ​The same error is continually reappearing under new forms—must be unmasked under all its disguises. preceding ones, several good reasons may be alleged for introducing them. The student of philosophy is never more perplexed than when he is brought into contact, again and again, with the same error expressed in different language, and with the same controversy carried on under an altered nomenclature. In such cases he is perplexed, because the new phraseology leads him to suppose that something different from what had formerly been before him is being treated of. When he knows that this is not something different, but the same, he is perplexed no longer. To obviate, therefore, this cause of embarrassment, it is proper to follow out the same error through all the disguises which it may assume, in order to show that, under all its aliases, it is merely an old acquaintance with a new face, or rather the same convict trying to impose upon us in a different dress. Error seems to be as tenacious of existence as truth. No sooner is it demolished under one form than it comes to life again under another. It steals, serpent-like, through the world, and, even when convicted, it usually escapes with the loss of little more than the mere skin upon its back. That is hung up in terrorem, but the wearer wanders on in another suit, wily, protean, and inexterminable. It is, therefore, the part of all well-wishers to the truth to keep a vigilant look-out upon the movements of this incorrigible vagrant,—to give notice of his approach, and to unmask him ​even when he is merely the same old offender calling himself by a different name.
Hence the necessity of Props. XVIII., XIX., XX., XXI.2. Conformably with the method adopted throughout these Institutes, this corrective plan can be carried into effect only by the enunciation of propositions which not only rectify the errors embodied in the corresponding counter-propositions, but also supply the truths which are recommended for acceptance in their stead. Error reiterated under new modes of expression must be met by new verbal reiterations of the truth adapted to these new verbal forms of falsity. Hence the propriety of introducing Props. XVIII., XIX., XX., XXI., which, although they are virtually identical with Props. XIV., XV., XVI., XVII., will be found to differ from them slightly in this respect, that they give a clearer expression both to the errors which are exposed, and to the truths which are advanced; and thus they contribute to the real improvement and final consummation of the science of metaphysics, which is, or ought to be, nothing but a continual working forwards from clearness to a greater and greater degree of insight, exactitude, and illumination in regard to all that concerns the higher interests and ultimate destiny of our nature.
3. Eighteenth Counter-proposition.—"There is ​Eighteenth counter-proposition.nothing but the relative in cognition: in other words, the relative, and the relative only, is known or knowable by man."
It is shown to be contradictory.4. The test of this counter-proposition is the definition just given of the relative. The relative can be known only along with its correlative: therefore to affirm that the relative only can be known, is to affirm that the relative can be known without its correlative being known, which, of course, is a contradictory assertion. What further fallacies lurk under this counter-proposition, and arise out of it, shall be exposed in the subsequent articles.