Simplikius farther observes (p. 65, b. 14) that Aristotle is not accurate in making [Greek: e)pistêto\n] correlate with [Greek: e)pistê/mê]: that in Relata, the potential correlates with the potential, and the actual with the actual. The Cognoscible is correlative, not with actual cognition ([Greek: e)pistê/mê]) but with potential Cognition, or with a potential Cognoscens. Aristotle therefore is right in saying that there may be [Greek: e)pistêto\n] without [Greek: e)pistê/mê], but this does not prove what he wishes to establish. Themistius, in another passage of the Aristotelian Scholia, reasoning against Boethus, observes to the same effect as Simplikius, that in relatives, the actual correlates with the actual, and the potential with the potential:-- [Greek: Kai/toi, phêsi/ ge o( Boêtho/s, ou)de\n kôlu/ei to\n a)rithmo\n ei)=nai kai\ di/cha tou= a)rithmou=ntos, ô(/sper oi)=mai to\ ai)sthêto\n kai\ di/cha tou= ai)sthanome/nou; spha/lletai de/, a(/ma ga\r ta\ pro\s ti/, kai\ ta\ duna/mei pro\s ta\ duna/mei; ô(/ste ei) mê\ kai\ a)rithmêtiko/n, ou)de\ to\ a)rithmêto/n] (Schol. ad Aristot. Physic. iv. p. 223, a. p. 393, Schol. Brandis). Compare Aristotel. Metaphysic. M. 1087, a. 15, about [Greek: to\ e)pi/stasthai duna/mei] and [Greek: to\ e)pi/stasthai e)nergei/a|]. About the essential co-existence of relatives--Sublato uno, tollitur alterum--see also Sextus Empiric. adv. Mathematicos, vii. 395, p. 449, Fabric.] [Side-note: Evidence from Plato proving implication of Subject and Object, in regard to the intelligible world.] That this general doctrine is true, not merely respecting the facts of sense, but also respecting the facts of mental conception, opinion, intellection, cognition--may be seen by the reasoning of Plato himself in other dialogues. How, for example, does Plato prove, in his Timæus, the objective reality of Ideas or Forms? He infers them from the subjective facts of his own mind. The subjective fact called Cognition (he argues) is generically different from the subjective fact called True Opinion: therefore the Object correlating with the One must be distinct from the Object correlating with the other: there must be a Noumenon or [Greek: noêto/n ti] correlating with Nous, distinct from the [Greek: doxasto/n ti] which correlates with [Greek: do/xa].[22] So again, in the Phædon,[23] Sokrates proves the pre-existence of the human soul from the fact that there were pre-existent cognizable Ideas: if there were knowable Objects, there must also have been a Subject Cognoscens or Cognitionis capax. The two are different aspects of one and the same conception: upon which we may doubtless reason abstractedly under one aspect or under the other, though they cannot be separated in fact. Now Both these two inferences of Plato rest on the assumed implication of Subject and Object.[24] [Footnote 22: Plato, Timæus, p. 51 B-E, compare Republic, v. p. 477.