Book VI appears to have in view two aims: (1) to describe goodness of intellect and discover its highest form or forms; (2) to show how this is related to goodness of character, and so to conduct generally. As all thinking is either theoretical or practical, goodness of intellect has two supreme forms—Theoretical and Practical Wisdom. The first, which apprehends the eternal laws of the universe, has no direct relation to human conduct: the second is identical with that master science of human life of which the whole treatise, consisting of the Ethics and the Politics, is an exposition. It is this science which supplies the right rules of conduct. Taking them as they emerge in and from practical experience, it formulates them more precisely and organises them into a system where they are all seen to converge upon happiness. The mode in which such knowledge manifests itself is in the power to show that such and such rules of action follow from the very nature of the end or good for man. It presupposes and starts from a clear conception of the end and the wish for it as conceived, and it proceeds by a deduction which is deliberation writ large. In the man of practical wisdom this process has reached its perfect result, and the code of right rules is apprehended as a system with a single principle and so as something wholly rational or reasonable. He has not on each occasion to seek and find the right rule applicable to the situation, he produces it at once from within himself, and can at need justify it by exhibiting its rationale, i.e. , its connection with the end. This is the consummate form of reason applied to conduct, but there are minor forms of it, less independent or original, but nevertheless of great value, such as the power to think out the proper cause of policy in novel circumstances, or the power to see the proper line of treatment to follow in a court of law.
The form of the thinking which enters into conduct is that which terminates in the production of a rule which declares some means to the end of life. The process presupposes (a) a clear and just apprehension of the nature of that end—such as the Ethics itself endeavours to supply; (b) a correct perception of the conditions of action. (a) at least is impossible except to a man whose character has been duly formed by discipline; it arises only in a man who has acquired moral virtue. For such action and feeling as forms bad character, blinds the eye of the soul and corrupts the moral principle, and the place of practical wisdom is taken by that parody of itself which Aristotle calls "cleverness"—the "wisdom" of the unscrupulous man of the world. Thus true practical wisdom and true goodness of character are interdependent; neither is genuinely possible or "completely" present without the other. This is Aristotle's contribution to the discussion of the question, so central in Greek Moral Philosophy, of the relation of the intellectual and the passionate factors in conduct.
Aristotle is not an intuitionist, but he recognises the implication in conduct of a direct and immediate apprehension both of the end and of the character of his circumstances under which it is from moment to moment realised. The directness of such apprehension makes it analogous to sensation or sense-perception; but it is on his view in the end due to the existence or activity in man of that power in him which is the highest thing in his nature, and akin to or identical with the divine nature—mind, or intelligence. It is this which reveals to us what is best for us—the ideal of a happiness which is the object of our real wish and the goal of all our efforts. But beyond and above the practical ideal of what is best for man begins to show itself another and still higher ideal—that of a life not distinctively human or in a narrow sense practical, yet capable of being participated in by man even under the actual circumstances of this world. For a time, however, this further and higher ideal is ignored.
The next book (Book VII), is concerned partly with moral conditions, in which the agent seems to rise above the level of moral virtue or fall below that of moral vice, but partly and more largely with conditions in which the agent occupies a middle position between the two. Aristotle's attention is here directed chiefly towards the phenomena of "Incontinence," weakness of will or imperfect self-control. This condition was to the Greeks a matter of only too frequent experience, but it appeared to them peculiarly difficult to understand. How can a man know what is good or best for him, and yet chronically fail to act upon his knowledge? Socrates was driven to the paradox of denying the possibility, but the facts are too strong for him. Knowledge of the right rule may be present, nay the rightfulness of its authority may be acknowledged, and yet time after time it may be disobeyed; the will may be good and yet overmastered by the force of desire, so that the act done is contrary to the agent's will. Nevertheless the act may be the agent's, and the will therefore divided against itself. Aristotle is aware of the seriousness and difficulty of the problem, but in spite of the vividness with which he pictures, and the acuteness with which he analyses, the situation in which such action occurs, it cannot be said that he solves the problem. It is time that he rises above the abstract view of it as a conflict between reason and passion, recognising that passion is involved in the knowledge which in conduct prevails or is overborne, and that the force which leads to the wrong act is not blind or ignorant passion, but always has some reason in it. But he tends to lapse back into the abstraction, and his final account is perplexed and obscure. He finds the source of the phenomenon in the nature of the desire for bodily pleasures, which is not irrational but has something rational in it. Such pleasures are not necessarily or inherently bad, as has sometimes been maintained; on the contrary, they are good, but only in certain amounts or under certain conditions, so that the will is often misled, hesitates, and is lost.
Books VIII and IX (on Friendship) are almost an interruption of the argument. The subject-matter of them was a favourite topic of ancient writers, and the treatment is smoother and more orderly than elsewhere in the Ethics. The argument is clear, and may be left without comment to the readers. These books contain a necessary and attractive complement to the somewhat dry account of Greek morality in the preceding books, and there are in them profound reflections on what may be called the metaphysics of friendship or love.
At the beginning of Book X we return to the topic of Pleasure, which is now regarded from a different point of view. In Book VII the antagonists were those who over-emphasised the irrationality or badness of Pleasure: here it is rather those who so exaggerate its value as to confuse or identify it with the good or Happiness. But there is offered us in this section much more than criticism of the errors of others. Answers are given both to the psychological question, "What is Pleasure?" and to the ethical question, "What is its value?" Pleasure, we are told, is the natural concomitant and index of perfect activity, distinguishable but inseparable from it—"the activity of a subject at its best acting upon an object at its best." It is therefore always and in itself a good, but its value rises and falls with that of the activity with which it is conjoined, and which it intensifies and perfects. Hence it follows that the highest and best pleasures are those which accompany the highest and best activity.
Pleasure is, therefore, a necessary element in the best life, but it is not the whole of it nor the principal ingredient. The value of a life depends upon the nature and worth of the activity which it involves; given the maximum of full free action, the maximum of pleasure necessary follows. But on what sort of life is such activity possible? This leads us back to the question, What is Happiness? In what life can man find the fullest satisfaction for his desires? To this question Aristotle gives an answer which cannot but surprise us after what has preceded. True Happiness, great satisfaction, cannot be found by man in any form of "practical" life, no, not in the fullest and freest exercise possible of the "moral virtues," not in the