Having assumed as one of the items of his definition, that man's happiness must be in his special or characteristic work, performed with perfect excellence,--Aristotle now proceeds to settle wherein that excellence consists. This leads to a classification of the parts of the soul. The first distribution is, into Rational and Irrational; whether these two are separable in fact, or only logically separable (like concave and convex), is immaterial to the present enquiry. Of the irrational, the lowest portion is the Vegetative [Greek: phytikon], which seems most active in sleep; a state where bad men and good are on a par, and which is incapable of any human excellence. The next portion is the Appetitive [Greek: epithymaetikon], which is not thus incapable. It partakes of reason, yet it includes something conflicting with reason. These conflicting tendencies are usually modifiable by reason, and may become in the temperate man completely obedient to reason. There remains Reason--the highest and sovereign portion of the soul. Human excellence [Greek: aretae] or virtue, is either of the Appetitive part,--moral [Greek: aethikae] virtue; or of the Reason--intellectual [Greek: dianoaetikae] virtue. Liberality and temperance are Moral virtues; philosophy, intelligence, and wisdom, Intellectual (XIII.). Such is an outline of the First Book, having for its subject the Chief Good, the Supreme End of man. Book Second embraces the consideration of points relative to the Moral Virtues; it also commences Aristotle's celebrated definition and classification of the virtues or excellencies.