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. [Footnote 20: See M. Jouffroy, Préface à sa Traduction des OEuvres de Reid, pp. xcvii.-ccxiv.