In an Appendix to this Dissertation, contained in the same volume (p. 608), Sir W. Hamilton not only re-asserts the doctrine ("Our whole knowledge of mind and matter is relative, conditioned--relatively conditioned. Of things absolutely or in themselves, be they external, be they internal, we know nothing, or know them only as incognisable," &c.)--but affirms farther that philosophers of every school, with the exception of a few late absolute theorisers in Germany, have always held and harmoniously re-echoed the same doctrine. In proof of such unanimous agreement, he cites passages from seventeen different philosophers. The first name on his list stands as follows:--"1. Protagoras--(as reported by Plato, Aristotle, Sextus Empiricus, Diogenes Laertius, &c.)--Man is (for himself) the measure of all things". Sir William Hamilton understands the Protagorean doctrine as I understand it, and as I have endeavoured to represent it in the present chapter. It has been very generally misconceived. I cannot, however, agree with Sir William Hamilton, in thinking that this theory respecting the Unconditioned and the Absolute, has been the theory generally adopted by philosophers. The passages which he cites from other authors are altogether insufficient to prove such an affirmation.] [Footnote 46: Plato, Theætêt. p. 156 A. [Greek: tê=s de\ kinê/seôs du/o ei)/dê, plê/thei me\n a)/peiron e(ka/teron, du/namin de\ to\ me\n poiei=n e)/chon, to\ de\ pa/schein.]] [Footnote 47: In that distinction, upon which Aristotle lays so much stress, between Actus and Potentia, he declares Actus or actuality to be the Prius--Potentia or potentiality to be the Posterius. See Metaphysica, [Greek: Th]. 8, 1049, b. 5 seqq.; De Animâ, ii. 4, 415, a. 17. The Potential is a derivative from the Actual--derived by comparison, abstraction, and logical analysis: a Mental concept, helping us to describe, arrange, and reason about, the multifarious acts of sense or consciousness--but not an anterior generating reality. Turgot observes (OEuvres, vol. iii. pp. 108-110; Article in the Encyclopédie, _Existence_):-- "Le premier fondement de la notion de l'_existence_ est la conscience de notre propre sensation, et le sentiment du _moi_ qui résulte de cette conscience. La relation nécessaire entre l'être appercevant, et l'être apperçu considéré hors du _moi_, suppose dans les deux termes la même réalité. Il y a dans l'un et dans l'autre un fondement de cette relation, que l'homme, s'il avoit un langage, pourroit désigner par le nom commun d'_existence_ ou de _présence_: car ces deux notions ne seroient point encore distinguées l'une de l'autre. . . .