Extracted from the MS. Commentary of Proclus on Alcibiades; excepting some occasional elucidations by the translator (Thomas Taylor).
The most peculiar and firm principle, says Proclus, of all the dialogues of Plato, and of the whole theory of that philosopher, is the knowledge of our own nature; for, this being properly established as an hypothesis, we shall be able accurately to learn the good which is adapted to us, and the evil which opposes this good. For, as the essences of things are different, so also are their proper perfections; and this according to a subjection of essence. For, whether being and The Good proceed, as Aristotle says, from the same Vesta and first fountain, it is certainly necessary that perfection should be imparted to every thing according to the measures of essence; or whether good proceeds from a cause more ancient and more characterized by unity, but essence and being are imparted to things from another cause; still, as every thing participates of being more obscurely and more clearly, in the same degree must it participate of good; first beings, in a greater and more perfect manner; but those that rank in the middle orders, secondarily; and the last of things according to an ultimate subsistence. For, how otherwise, can things participate of deity and providence, and a distribution according to their desert? For it must not be admitted that intellect can lead things into order, and impart to each a convenient measure, but that The Good, or the ineffable principle of things, which is more ancient than intellect, should make its communications in a disordered manner; viz. that it should impart causes and things caused the same portion of goodness, and distribute to the same things according to being the perfections of more primary and subordinate natures. For it neither was lawful, says Timaeus ([[Tim:30a|30a-b]]), nor is, for the best of natures to effect any thing but that which is most beautiful and most commensurate. But the same good is not most commensurate to first and secondary natures; but, as the Athenian guest says, a distribution of inequality to things unequal, and of equality to things equal, of the greater to such as are greater, and of the lesser to such as are lesser, is of all things the most musical and the best. ([[Laws:757a|Laws 757a]])
According to this reasoning, therefore, good is different in different beings, and a certain good is naturally coordinated to the essence of every thing. Hence the perfection of intellect is in eternity,1 but of the rational soul in time: and the good of the rational soul consists in an energy according to intellect, but the good of body is in a subsistence according to nature; so that he who thinks that though the nature in these is different, yet the perfection is the same, has an erroneous conception of the truth of things.
According to every order of beings, therefore, essence ought to be known prior to perfection; for perfection is not of itself, but of essence, by which it is participated. Hence, with respect to the essence of a thing, we must first consider whether it belongs to impartible essences, such as intellectual natures, or to such as are divisible about bodies, viz. corporeal forms and qualities, or to such as subsist between these. Likewise, whether it ranks among eternal entities, or such as subsist according to the whole of time, or such as are generated in a certain part of time. Again, whether it is simple, and subsists prior to composition, or is indeed a composite, but is always in the act of being bound with indissoluble bonds,2 or may again be resolved into those things from which it is composed. For, by thus considering every thing, we shall be able to understand in what its good consists. For, again, it is evident that the good of those natures which are allotted an impartible essence is eternal, but that the good of partible natures is conversant with time and motion; and that the good of things subsisting between these is to be considered according to the measures of subsistence and perfection; viz. that such a nature is indeed indigent of time, but of first time, which is able to measure incorporeal periods. So that the pure and genuine knowledge of ourselves, circumscribed in scientific boundaries, must, as we have said, be considered as the most proper principle of all philosophy, and of the doctrine of Plato. For, where is it proper to begin, except from the purification and perfection of ourselves, and whence the Delphic god exhorts us to begin? For, as those who enter the Eleusinian grove are ordered by an inscription not to enter into the adyta of the temple, if they are uninitiated in the highest of the mysteries, so the inscription KNOW THYSELF, on the Delphic temple, manifests, as it appears to me, the mode of returning to a divine nature, and the most useful path to purification, all but perspicuously asserting to the intelligent, that he who knows himself beginning from the Vestal hearth may be able to be conjoined with that divinity who unfolds into light the whole of truth, and is the leader of a cathartic life; but that he who is ignorant of himself, as being uninitiated both in the lesser and greater mysteries, is unadapted to participate the providence of Apollo. Hence then let us also begin conformably to the mandate of the god, and let us investigate in which of his dialogues Plato especially makes the speculation of our essence his principal design, that from hence we may also make the commencement of the Platonic writings. Can we than adduce any other writing of Plato except the First Alcibiades, and the conference of Socrates which is delivered in this dialogue? Where else shall we say our essence is unfolded? Where besides are man and the nature of man investigated? To which we may add, that it is Socrates who engages in this first conversation with Alcibiades, and that it is he who says that the beginning of perfection is suspended from the contemplation of ourselves. For we are ignorant of ourselves in consequence of being involved in oblivion produced in the realms of generation, and agitated by the tumult of the irrational forms of life. In the mean time, we think that we know many things of which we are ignorant, because we essentially possess innate reasons of things.