Perpetual implication of Subject with Object — Relate and Correlate.
In declaring that “Man is the measure of all things” — Protagoras affirms that Subject is the measure of Object, or that every object is relative to a correlative Subject. When a man affirms, believes, or conceives, an object as existing, his own believing or concipient mind is one side of the entire fact. It may be the dark side, and what is called the Object may be the light side, of the entire fact: this is what happens in the case of tangible and resisting substances, where Object, being the light side of the fact, is apt to appear all in all:[19] a man thinks of the Something which resists, without attending to the other aspect of the fact of resistance, viz.: his own energy or pressure, to which resistance is made. On the other hand, when we speak of enjoying any pleasure or suffering any pain, the enjoying or suffering Subject appears all in all, distinguished plainly from other Subjects, supposed to be not enjoying or suffering in the same way: yet it is no more than the light side of the fact, of which Object is the dark side. Each particular pain which we suffer has its objective or differential peculiarity, distinguishing it from other sensations, correlating with the same sentient Subject.
[19] “Nobiscum semper est ipsa quam quærimus (anima); adest, tractat, loquitur — et, si fas est dicere, inter ista nescitur.” (Cassiodorus, De Animâ, c. 1, p. 594, in the edition of his Opera Omnia, Venet. 1729).
“In the primitive dualism of consciousness, the Subject and Object being inseparable, either of them apart from the other must be an unknown quantity: the separation of either must be the annihilation of both.” (F. W. Farrar, Chapters on Language, c. 23, p. 292: which chapter contains more on the same topic, well deserving of perusal.)
Such relativity is no less true in regard to the ratiocinative combinations of each individual, than in regard to his percipient capacities.
The Protagorean dictum will thus be seen, when interpreted correctly, to be quite distinct from that other doctrine with which Plato identifies it: that Cognition is nothing else but sensible Perception. If, rejecting this last doctrine, we hold that cognition includes mental elements distinct from, though co-operating with, sensible perception — the principle of relativity laid down by Protagoras will not be the less true. My intellectual activity — my powers of remembering, imagining, ratiocinating, combining, &c., are a part of my mental nature, no less than my powers of sensible perception: my cognitions and beliefs must all be determined by, or relative to, this mental nature: to the turn and development which all these various powers have taken in my individual case. However multifarious the mental activities may be, each man has his own peculiar allotment and manifestations thereof, to which his cognitions must be relative. Let us grant (with Plato) that the Nous or intelligent Mind apprehends intelligible Entia or Ideas distinct from the world of sense: or let us assume that Kant and Reid in the eighteenth century, and M. Cousin with other French writers in the nineteenth, have destroyed the Lockian philosophy, which took account (they say) of nothing but the à posteriori element of cognition — and have established the existence of other elements of cognition à priori: intuitive beliefs, first principles, primary or inexplicable Concepts of Reason.[20] Still we must recollect that all such à priori Concepts, Intuitions, Beliefs, &c., are summed up in the mind: and that thus each man’s mind, with its peculiar endowments, natural or supernatural, is still the measure or limit of his cognitions, acquired and acquirable. The Entia Rationis exist relatively to Ratio, as the Entia Perceptionis exist relatively to Sense. This is a point upon which Plato himself insists, in this very dialogue. You do not, by producing this fact of innate mental intuitions, eliminate the intuent mind; which must be done in order to establish a negative to the Protagorean principle.[21] Each intuitive belief whether correct or erroneous — whether held unanimously by every one semper et ubique, or only held by a proportion of mankind — is (or would be, if proved to exist) a fact of our nature; capable of being looked at either on the side of the believing Subject, which is its point of community with all other parts of our nature — or on the side of the Object believed, which is its point of difference or peculiarity. The fact with its two opposite aspects is indivisible. Without Subject, Object vanishes: without Object (some object or other, for this side of the fact is essentially variable), Subject vanishes.
[20] See M. Jouffroy, Préface à sa Traduction des Œuvres de Reid, pp. xcvii.-ccxiv.
M. Jouffroy, following in the steps of Kant, declares these à priori beliefs or intuitions to be altogether relative to the human mind. “Kant, considérant que les conceptions de la raison sont des croyances aveugles auxquelles notre esprit se sent fatalement déterminé par sa nature, en conclut qu’elles sont rélatives à cette nature: que si notre nature était autre, elles pourraient être différentes: que par conséquent, elles n’ont aucune valeur absolue: et qu’ainsi notre vérité, notre science, notre certitude, sont une vérité, une science, une certitude, purement subjective, purement humaine — à laquelle nous sommes déterminés à nous fier par notre nature, mais qui ne supporte pas l’examen et n’a aucune valeur objective” (p. clxvii.) … “C’est ce que répéte Kant quand il soutient que l’on ne peut objectiver le subjectif: c’est à dire, faire que la vérité humaine cesse d’être humaine, puisque la raison qui la trouve est humaine. On peut exprimer de vingt manières différentes cette impossibilité: elle reste toujours la même, et demeure toujours insurmontable,” p. cxc. Compare p. xcvii. of the same Preface.
M. Pascal Galuppi (in his Lettres Philosophiques sur les Vicissitudes de la Philosophie, translated from the Italian by M. Peisse, Paris, 1844) though not agreeing in this variety of à priori philosophy, agrees with Kant in declaring the à priori element of cognition to be purely subjective, and the objective element to be à posteriori (Lett. xiv. pp. 337-338), or the facts of sense and experience. “L’ordre à priori, que Kant appelle transcendental, est purement idéal, et dépourvu de toute réalité. Je vis, qu’en fondant la connaissance sur l’ordre à priori, on arrive nécessairement au scepticisme: et je reconnus que la doctrine Écossaise est la mère légitime du Criticisme Kantien, et par conséquent, du scepticisme, qui est la conséquence de la philosophie critique. Je considérai comme de haute importance ce problème de Kant. Il convient de déterminer ce qu’il y a d’objectif, et ce qu’il y a de subjectif, dans la connaissance. Les Empiriques n’admettent dans la connaissance d’autres élémens que les objectifs,” &c.
[21] See this point handled in Sextus Empiric. adv. Mathemat. viii. 355-362. We may here cite a remark of Simplikius in his Commentary on the Categories of Aristotle (p. 64, a. in Schol. Brandis). Aristotle (De Animâ, iii. 2, 426, a. 19; Categor. p. 7, b. 23) lays down the doctrine that in most cases Relata or (τὰ πρός τι) are “simul Naturâ, καὶ συναναιρεῖ ἄλληλα”: but that in some Relata this is not true: for example, τὸ ἐπιστητὸν is relative to ἐπιστήμη, yet still it would seem prior to ἐπιστήμη (πρότερον ἂν δόξειε τῆς ἐπιστήμης εἶναι). There cannot be ἐπιστήμη without some ἐπιστητόν: but there may be ἐπιστητὸν without any ἐπιστήμη. There are few things, if any (he says), in which the ἐπιστητὸν (cognoscibile) is simul naturâ with ἐπιστήμη (or cognitio) and cannot be without it.