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. [Footnote 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.)] [Side-note: Such relativity is no less true in regard to the ratiocinative combinations of each individual, than in regard to his percipient capacities.]