Ens alone can be known — Non-Ens is unknowable. That which is midway between Ens and Non-Ens (particulars) is matter only of opinion. Ordinary men attain nothing beyond opinion.
This latter, the unphilosophical man, will not admit what we say. Accordingly, we must prove it to him. You cannot know without knowing Something: that is, Some Ens: for Non-Ens cannot be known. That which is completely and absolutely Ens, is completely and absolutely cognizable: that which is Non-Ens and nowhere, is in every way uncognizable. If then there be anything which is at once Ens and Non-Ens, it will lie midway between these two: it will be something neither absolutely and completely cognizable, nor absolutely and completely uncognizable: it belongs to something between ignorance and science. Now science or knowledge is one thing, its object is, complete Ens. Opinion is another thing, its object also is different. Knowing and Opining belong, like Sight and Hearing, to the class of Entia called Powers or Faculties, which we and others possess, and by means of which — that is, by means of one or other of them — we accomplish everything that we do accomplish. Now no one of these powers or faculties has either colour or figure, whereby it may be recognised or distinguished from others. Each is known and distinguished, not by what it is in itself, but by what it accomplishes, and by the object to which it has special relation. That which has the same object and accomplishes the same result, I call the same power or faculty: that which has a different object, and accomplishes a different result, I call a different power or faculty. Now Knowing, Cognition, Science, is one of our faculties or powers, and the strongest of all: Opining is another, and a different one. A marked distinction between the two is, that Knowing or Cognition is infallible — Opining is fallible. Since Cognition is one power or faculty, and Opining another — the object of one must be different from the object of the other. But the object of Cognition is, the Complete Ens: the object of Opining must therefore be, not the Complete Ens, but something different from it. What then is the object of Opining? It is not Complete Ens, but it is still Something. It is not Non-Ens, or Nothing; for Non-Ens or Nothing is not thinkable or opinable: you cannot think or opine, and yet think or opine nothing. Whoever opines or thinks, must opine or think something. Ens is the object of Cognition, Non-Ens is the object of non-Cognition or Ignorance: Opination or Opinion is midway between Cognition and Ignorance, darker than the former, but clearer than the latter. The object of opination is therefore something midway between Ens and Non-Ens.
Particulars fluctuate: they are sometimes just or beautiful, sometimes unjust or ugly. Forms or Entia alone remain constant.
But what is this Something, midway between Ens and Particulars Non-Ens, and partaking of both — which is the object of Opination? To make out this, we must revert to the case of the unphilosophical man. We have described him, as not believing in the existence of the Form or Idea of Beauty, or Justice per se; not enduring to hear it spoken of as a real Ens and Unum; not knowing anything except of the many diverse particulars, beautiful and just. We must remind him that every one of these particular beautiful things will appear repulsive also: every one of these just and holy particulars, will appear unjust and unholy also. He cannot refuse to admit that each of them will appear under certain circumstances beautiful and ugly, just and unjust, holy and unholy. In like manner, every particular double will appear also a half: every light thing will appear heavy: every little thing great. Of each among these many particulars, if you can truly predicate any one quality about it, you may with equal truth predicate the opposite quality also. Each of them both is, and is not, the substratum of all these different and opposite qualities. You cannot pronounce them to be either one or the other, with fixity and permanence: they are at once both and neither.
The many cannot discern or admit the reality of Forms — Their minds are always fluctuating among particulars.
Here then we find the appropriate object of Opination: that which is neither Ens nor Non-Ens, but something between both. Particulars are the object of Opination, as distinguished from universal Entities, Forms, or Ideas, which are the object of Cognition. The many, who disbelieve or ignore the existence of these Forms, and whose minds dwell exclusively among particulars — cannot know, but only opine. Their usages and creeds, as to beautiful, just, honourable, float between positive Ens and Non-Ens. It is these intermediate fluctuations which are caught up by their opining faculty, intermediate as it is between Cognition and Ignorance. It is these also, the objects of Opination, which they love and delight in: they neither recognise nor love the objects of Cognition or Knowledge. They are lovers of opinion and its objects, not lovers of Knowledge. The philosopher alone recognises and loves Knowledge and the objects of Knowledge. His mind dwells, not amidst the fluctuating, diverse, and numerous particulars, but in contemplation of the One, Universal, permanent, unchangeable, Form or Idea.
The philosopher will be ardent for all varieties of knowledge — His excellent moral attributes — He will be trained to capacity for active life.
Here is the characteristic difference (continues Sokrates) which you required me to point out, between the philosopher and the unphilosophical man, however accomplished. The philosopher sees, knows, and contemplates, the One, Real, unchangeable, Form or Idea: the unphilosophical man knows nothing of this Form per se, and sees only its multifarious manifestations, each perpetually variable and different from all the rest. The philosopher, having present to his mind this type — and approximating to it, as far as may be, the real institutions and practices — will be the person most competent to rule our city: especially as his education will give him farthermore — besides such familiarity with the Form or Type — as large a measure of experience, and as much virtue, as can fall to the lot of the unphilosophical man.[151] The nature and disposition of the true philosopher, if improved by education, will include all the virtue and competence of the practical man. The philosopher is bent on learning everything which can make him familiar with Universal Forms and Essences in their pure state, not floating amidst the confusion of generated and destroyed realities: and with Forms and Essences little as well as great, mean as well as sublime.[152] Devoted to knowledge and truth — hating falsehood — he has little room in his mind for the ordinary desires: he is temperate, indifferent to money, free from all meanness or shabbiness. A man like him, whose contemplations stretch over all time and all essence, thinks human life a small affair, and has no fear of death. He will be just, mild in his demeanour, quick in apprehension, retentive in memory, elegant in his tastes and movements. All these excellences will be united in the philosophers to whom we confide the rule of our city.[153]
[151] Plato, Republic, vi. p. 484.
[152] Plato, Republic, vi. p. 485 A.