In specifying the ethical excellences, or excellences of disposition, we explained that each of them aimed to realize a mean--and that this mean was to be determined by Right Reason. To find the mean, is thus an operation of the Intellect; and we have now to explain what the right performance of it is,--or to enter upon the Excellences of the Intellect. The soul having been divided into Irrational and Rational, the Rational must farther be divided into two parts,--the Scientific (dealing with necessary matter), the Calculative, or Deliberative (dealing with contingent matter). We must touch, upon the excellence or best condition of both of them (I). There are three principal functions of the soul--Sensation, Reason, and Appetite or Desire. Now, Sensation (which beasts have as well as men) is not a principle of moral action. The Reason regards truth and falsehood only; it does not move to action, it is not an end in itself. Appetite or Desire, which aims at an end, introduces us to moral action. Truth and Falsehood, as regards Reason, correspond to Good and Evil as regards Appetite: Affirmation and Negation, with the first, are the analogues of Pursuit and Avoidance, with the second. In purpose, which is the principle of moral action, there is included deliberation or calculation. Reason and Appetite are thus combined: Good Purpose comprises both true affirmation and right pursuit: you may call it either an Intelligent Appetite, or an Appetitive Intelligence. Such is man, as a principle of action [hae toiautae archae anthropos].
Science has to do with the necessary and the eternal; it is teachable, but teachable always from _praecognita_, or principles, obtained by induction; from which principles, conclusions are demonstrated by syllogism (III.). Art, or Production, is to be carefully distinguished from the action or agency that belongs to man as an ethical agent, and that does not terminate in any separate assignable product. But both the one and the other deal with contingent matters only. Art deals for the most part with the same matters as are subject to the intervention of Fortune or Chance (IV.).
Prudence or Judiciousness [Greek: phronaesis], the quality of [Greek: ho phronimos], the Practical Reason, comes next. We are told what are the matters wherewith it is, and wherewith it is not, conversant. It does not deal with matters wherein there exist art, or with rules of art. It does not deal with necessary matters, nor with matters not modifiable by human agency. The prudent or judicious man is one who (like Pericles) can accurately estimate and foresee matters (apart from Science and Art) such as are good or evil for himself and other human beings. On these matters, feelings of pleasure or pain are apt to bias the mind, by insinuating wrong aims; which they do not do in regard to the properties of a triangle and other scientific conclusions. To guard against such bias, the judicious man must be armed with the ethical excellence described above as Temperance or Moderation. Judiciousness is not an Art, admitting of better and worse; there are not good judicious men, and bad judicious men, as there are good and bad artists. Judiciousness is itself an excellence (_i.e._, the term connotes excellence)--an excellence of the rational soul, and of that branch of the rational soul which is calculating, deliberative, not scientific (V.). Reason or Intellect [Greek: nous] is the faculty for apprehending the first principles of demonstrative science. It is among the infallible faculties of the mind, together with Judiciousness, Science, and Philosophy. Each of these terms connotes truth and accuracy (VI.). Wisdom in the arts is the privilege of the superlative artists, such as Phidias in sculpture. But there are some men wise, not in any special art, but absolutely; and this wisdom [Greek: sophia] is Philosophy. It embraces both principles of science (which Aristotle considers to come under the review of the First Philosophy) and deductions therefrom; it is [Greek: nous] and [Greek: epistaemae] in one. It is more venerable and dignified than Prudence or Judiciousness; because its objects, the Kosmos and the celestial bodies, are far more glorious than man, with whose interests alone Prudence is concerned; and also because the celestial objects are eternal and unvarying; while man and his affairs are transitory and ever fluctuating. Hence the great honour paid to Thales, Anaxagoras, and others, who speculated on theories thus magnificent and superhuman, though useless in respect to human good.