Book 61. We have already said1 that it is right to choose the mean and to avoid excess and deficiency, and that the mean is prescribed by the right principle. Let us now analyze the latter notion. In the case of each of the moral qualities or dispositions that have been discussed, as with all the other virtues also, there is a certain mark to aim at, on which the man who knows the principle involved fixes his gaze, and increases or relaxes the tension2 accordingly; there is a certain standard determining those modes of observing the mean which we define as lying between excess and defect, being in conformity with the right principle. 1.  This bare statement however, although true, is not at all enlightening. In all departments of human endeavor that have been reduced to a science, it is true to say that effort ought to be exerted and relaxed neither too much nor too little, but to the medium amount, and as the right principle decides. Yet a person knowing this truth will be no wiser than before: for example, he will not know what medicines to take merely from being told to take everything that medical science or a medical expert would prescribe. 1.  Hence with respect to the qualities of the soul also, it is not enough merely to have established the truth of the above formula; we also have to define exactly what the right principle is, and what is the standard that determines it.3 1.  Now we have divided the Virtues of the Soul into two groups, the Virtues of the Character and the Virtues of the Intellect. The former, the Moral Virtues, we have already discussed. Our account of the latter must be prefaced by some remarks about psychology.1.  It has been said before4 that the soul has two parts, one rational and the other irrational. Let us now similarly divide the rational part, and let it be assumed that there are two rational faculties, one whereby we contemplate those things whose first principles are invariable, and one whereby we contemplate those things which admit of variation: since, on the assumption that knowledge is based on a likeness or affinity of some sort between subject and object, the parts of the soul adapted to the cognition of objects that are of different kinds must themselves differ in kind. 1.  These two rational faculties may be designated the Scientific Faculty and the Calculative Faculty respectively; since calculation is the same as deliberation, and deliberation is never exercised about things that are invariable, so that the Calculative Faculty is a separate part of the rational half of the soul.1.  We have therefore to ascertain what disposition of each of these faculties is the best, for that will be the special virtue of each. But the virtue of a faculty is related to the special function which that faculty performs. 2. Now there are three elements in the soul which control action and the attainment of truth: namely, Sensation, Intellect,5 and Desire.2.  Of these, Sensation never originates action, as is shown by the fact that animals have sensation but are not capable of action.6 7Pursuit and avoidance in the sphere of Desire correspond to affirmation and denial in the sphere of the Intellect. Hence inasmuch as moral virtue is a disposition of the mind in regard to choice,8 and choice is deliberate desire,9 it follows that, if the choice is to be good, both the principle must be true and the desire right, and that desire must pursue the same things as principle affirms. 2.  We are here speaking of practical thinking, and of the attainment of truth in regard to action; with speculative thought, which is not concerned with action or production, right and wrong functioning consist in the attainment of truth and falsehood respectively. The attainment of truth is indeed the function of every part of the intellect, but that of the practical intelligence is the attainment of truth corresponding to right desire.10 2.  Now the cause of action （the efficient, not the final cause） is choice,11 and the cause of choice is desire and reasoning directed to some end. Hence choice necessarily involves both intellect or thought and a certain disposition of character [12 for doing well and the reverse in the sphere of action necessarily involve thought and character].2.  Thought by itself however moves nothing, but only thought directed to an end, and dealing with action. This indeed is the moving cause of productive activity13 also, since he who makes some thing always has some further end in view: the act of making is not an end in itself, it is only a means, and belongs to something else. Whereas a thing done is an end in itself: since doing well （welfare14） is the End, and it is at this that desire aims. Hence Choice may be called either thought related to desire or desire related to thought; and man, as an originator of action, is a union of desire and intellect.2.  （Choice is not concerned with what has happened already: for example, no one chooses to have sacked Troy; for neither does one deliberate about what has happened in the past, but about what still lies in the future and may happen or not; what has happened cannot be made not to have happened. Hence Agathon is right in saying “ This only is denied even to God,
The power to make what has been done undone.）
” The attainment of truth is then the function of both the intellectual parts of the soul. Therefore their respective virtues are those dispositions which will best qualify them to attain truth.3. Let us then discuss these virtues afresh, going more deeply into the matter. Let it be assumed that there are five qualities through which the mind achieves truth in affirmation or denial, namely Art or technical skill,15 Scientific Knowledge, Prudence, Wisdom, and Intelligence. Conception and Opinion are capable of error. 3.  The nature of Scientific Knowledge （employing the term in its exact sense and disregarding its analogous uses） may be made clear as follows. We all conceive that a thing which we know scientifically cannot vary; when a thing that can vary is beyond the range of our observation, we do not know whether it exists or not. An object of Scientific Knowledge, therefore, exists of necessity. It is therefore eternal, for everything existing of absolute necessity is eternal; and what is eternal does not come into existence or perish. 3.  Again, it is held that all Scientific Knowledge can be communicated by teaching, and that what is scientifically known must be learnt. But all teaching starts from facts previously known, as we state in the Analytics,16 since it proceeds either by way of induction, or else by way of deduction. Now induction supplies a first principle or universal, deduction works from universals; therefore there are first principles from which deduction starts, which cannot be proved by deduction; therefore they are reached by induction. 3.  Scientific Knowledge, therefore, is the quality whereby we demonstrate,17 with the further qualifications included in our definition of it in the Analytics,18 namely, that a man knows a thing scientifically when he possesses a conviction arrived at in a certain way, and when the first principles on which that conviction rests are known to him with certainty—for unless he is more certain of his first principles than of the conclusion drawn from them he will only possess the knowledge in question accidentally.19 Let this stand as our definition of Scientific Knowledge. 4. The class of things that admit of variation includes both things made and actions done.  But making is different from doing （a distinction we may accept from extraneous discourses20）. Hence the rational quality concerned with doing is different from the rational quality concerned with making; nor is one of them a part of the other, for doing is not a form of making, nor making a form of doing.  Now architectural skill, for instance, is an art, and it is also a rational quality concerned with making; nor is there any art which is not a rational quality concerned with making, nor any such quality which is not an art. It follows that an art is the same thing as a rational quality, concerned with making, that reasons truly.  All Art deals with bringing some thing into existence; and to pursue an art means to study how to bring into existence a thing which may either exist or not, and the efficient cause of which lies in the maker and not in the thing made; for Art does not deal with things that exist or come into existence of necessity, or according to nature, since these have their efficient cause in themselves.  But as doing and making are distinct, it follows that Art, being concerned with making, is not concerned with doing. And in a sense Art deals with the same objects as chance, as Agathon says: “ Chance is beloved of Art, and Art of Chance.
”  Art, therefore, as has been said, is a rational quality, concerned with making, that reasons truly. Its opposite, Lack of Art, is a rational quality, concerned with making, that reasons falsely. Both deal with that which admits of variation.5. We may arrive at a definition of Prudence by considering who are the persons whom we call prudent. Now it is held to be the mark of a prudent man to be able to deliberate well about what is good and advantageous for himself, not in some one department, for instance what is good for his health or strength, but what is advantageous as a means to the good life in general.  This is proved by the fact that we also speak of people as prudent or wise in some particular thing, when they calculate well with a view to attaining some particular end of value （other than those ends which are the object of an art）; so that the prudent man in general will be the man who is good at deliberating in general.  But no one deliberates about things that cannot vary, nor about things not within his power to do. Hence inasmuch as scientific knowledge involves demonstration, whereas things whose fundamental principles are variable are not capable of demonstration, because everything about them is variable, and inasmuch as one cannot deliberate about things that are of necessity, it follows that Prudence is not the same as Science. Nor can it be the same as Art. It is not Science, because matters of conduct admit of variation; and not Art, because doing and making are generically different,21 since making aims at an end distinct from the act of making, whereas in doing the end cannot be other than the act itself: doing well22 is in itself the end.  It remains therefore that it is a truth-attaining rational quality, concerned with action in relation to things that are good and bad for human beings.  Hence men like Pericles are deemed prudent, because they possess a faculty of discerning what things are good for themselves and for mankind and that is our conception of an expert in Domestic Economy or Political Science. （This also accounts for the word Temperance,23 which signifies ‘preserving prudence.’  And Temperance does in fact preserve our belief as to our own good; for pleasure and pain do not destroy or pervert all beliefs, for instance, the belief that the three angles of a triangle are, or are not, together equal to two right angles, but only beliefs concerning action. The first principles of action are the end to which our acts are means; but a man corrupted by a love of pleasure or fear of pain, entirely fails to discern any first principle,24 and cannot see that he ought to choose and do everything as a means to this end, and for its sake; for vice tends to destroy the sense of principle.25） It therefore follows that Prudence is a truth-attaining rational quality, concerned with action in relation to the things that are good for human beings.  Moreover, we can speak of excellence in Art,26 but not of excellence in Prudence. Also in Art voluntary error is not so bad as involuntary, whereas in the sphere of Prudence it is worse, as it is in the sphere of the virtues. It is therefore clear that Prudence is an excellence or virtue, and not an Art.  Of the two parts of the soul possessed of reason, Prudence must be the virtue of one, namely, the part that forms opinions27; for Opinion deals with that which can vary, and so does Prudence. But yet Prudence is not a rational quality merely, as shown by the fact that a purely rational faculty can be forgotten, whereas a failure in Prudence is not a mere lapse of memory.28 6. Scientific Knowledge is a mode of conception dealing with universals and things that are of necessity; and demonstrated truths and all scientific knowledge （since this involves reasoning） are derived from first principles. Consequently the first principles from which scientific truths are derived cannot themselves be reached by Science; nor yet are they apprehended by Art, nor by Prudence. To be matter of Scientific Knowledge a truth must be demonstrated by deduction from other truths; while Art and Prudence are concerned only with things that admit of variation. Nor is Wisdom the knowledge of first principles either29: for the philosopher has to arrive at some things by demonstration.30  If then the qualities whereby we attain truth,31 and are never led into falsehood, whether about things invariable or things variable, are scientific Knowledge, Prudence, Wisdom, and Intelligence, and if the quality which enables us to apprehend first principles cannot be any one among three of these, namely Scientific Knowledge, Prudence, and Wisdom, it remains that first principles must be apprehended by Intelligence.32 7. The term Wisdom is employed in the arts to denote those men who are the most perfect masters of their art, for instance, it is applied to Pheidias as a sculptor and to Polycleitus as a statuary. In this use then Wisdom merely signifies artistic excellence.  But we also think that some people are wise in general and not in one department, not ‘wise in something else,’33 as Homer says in the Margites: “ Neither a delver nor a ploughman him
The Gods had made, nor wise in aught beside.
” Hence it is clear that Wisdom must be the most perfect of the modes of knowledge.  The wise man therefore must not only know the conclusions that follow from his first principles, but also have a true conception of those principles themselves. Hence Wisdom must be a combination of Intelligence and Scientific Knowledge34: it must be a consummated knowledge35 of the most exalted36 objects. For it is absurd to think that Political Science or Prudence is the loftiest kind of knowledge, inasmuch as man is not the highest thing in the world.  And as ‘wholesome’ and ‘good’ mean one thing for men and another for fishes, whereas ‘white’ and ‘straight’ mean the same thing always, so everybody would denote the same thing by ‘wise,’ but not by ‘prudent’; for each kind of beings will describe as prudent, and will entrust itself to, one who can discern its own particular welfare; hence even some of the lower animals are said to be prudent, namely those which display a capacity for forethought as regards their own lives. It is also clear that Wisdom cannot be the same thing as Political Science; for if we are to call knowledge of our own interests wisdom, there will be a number of different kinds of wisdom, one for each species: there cannot be a single such wisdom dealing with the good of all living things, any more than there is one art of medicine for all existing things. It may be argued that man is superior to the other animals, but this makes no difference: since there exist other things far more divine in their nature than man, for instance, to mention the most visible, the things37 of which the celestial system is composed.  These considerations therefore show that Wisdom is both Scientific Knowledge and Intuitive Intelligence as regards the things of the most exalted38 nature. This is why people say that men like Anaxagoras and Thales39 ‘may be wise but are not prudent,’ when they see them display ignorance of their own interests; and while admitting them to possess a knowledge that is rare, marvellous, difficult and even superhuman, they yet declare this knowledge to be useless, because these sages do not seek to know the things that are good for human beings.  Prudence on the other hand is concerned with the affairs of men, and with things that can be the object of deliberation. For we say that to deliberate well is the most characteristic function of the prudent man; but no one deliberates about things that cannot vary nor yet about variable things that are not a means to some end, and that end a good attainable by action; and a good deliberator in general is a man who can arrive by calculation at the best of the goods attainable by man.  Nor is Prudence a knowledge of general principles only: it must also take account of particular facts, since it is concerned with action, and action deals with particular things. This is why men who are ignorant of general principles are sometimes more successful in action than others who know them: 40 for instance, if a man knows that light meat is easily digested and therefore wholesome, but does not know what kinds of meat are light, he will not be so likely to restore you to health as a man who merely knows that chicken is wholesome; and in other matters men of experience are more successful than theorists. And Prudence is concerned with action, so one requires both forms of it, or indeed knowledge of particular facts even more than knowledge of general principles. Though here too there must be some supreme directing faculty.41 8. Prudence is indeed the same quality of mind as Political Science, though their essence is different.42  Of Prudence as regards the state, one kind, as supreme and directive, is called Legislative Science43; the other, as dealing with particular occurrences, has the name, Political Science, that really belongs to both kinds. The latter is concerned with action and deliberation （for a parliamentary enactment is a thing to be done, being the last step44 in a deliberative process）, and this is why it is only those persons who deal with particular facts who are spoken of as ‘taking part in politics,’ because it is only they who perform actions, like the workmen in an industry.45  Prudence also is commonly understood to mean especially that kind of wisdom which is concerned with oneself, the individual; and this is given the name, Prudence, which really belongs to all the kinds, while the others are distinguished as Domestic Economy, Legislature, and Political Science, the latter being subdivided into Deliberative Science and Judicial Science.  Now knowledge of one's own interest will certainly be one kind of Prudence; though it is very different from the other kinds, and people think that the man who knows and minds his own business is prudent, and that politicians are busybodies: thus Euripides writes— “ Would that be prudent? when I might have lived
A quiet life, a cipher in the crowd,
Sharing the common fortune. . .
Restless, aspiring, busy men of action. . .
”46 For people seek their own good, and suppose that it is right to do so. Hence this belief has caused the word ‘prudent’ to mean those who are wise in their own interest. Yet probably as a matter of fact a man cannot pursue his own welfare without Domestic Economy and even Politics. Moreover, even the proper conduct of one's own affairs is a difficult problem, and requires consideration.  A further proof of what has been said47 is, that although the young may be experts in geometry and mathematics and similar branches of knowledge, we do not consider that a young man can have Prudence. The reason is that Prudence includes a knowledge of particular facts, and this is derived from experience, which a young man does not a possess;  for experience is the fruit of years.48 （One might indeed further enquire why it is that, though a boy may be a mathematician, he cannot be a metaphysician or a natural philosopher.49 Perhaps the answer is that Mathematics deals with abstractions, whereas the first principles of Metaphysics and Natural Philosophy are derived from experience: the young can only repeat them without conviction of their truth,50 whereas the formal concepts of Mathematics are easily understood.）  Again, in deliberation there is a double possibility of error: you may go wrong either in your general principle or in your particular fact: for instance, either in asserting that all heavy water is unwholesome, or that the particular water in question is heavy.  And it is clear that Prudence is not the same as Scientific Knowledge: for as has been said, it apprehends ultimate particular things, since the thing to be done is an ultimate particular thing.51  Prudence then stands opposite to Intelligence; for Intelligence52 apprehends definitions, which cannot be proved by reasoning, while Prudence deals with the ultimate particular thing, which cannot be apprehended by Scientific Knowledge, but only by perception: not the perception of the special senses,53 but the sort of intuition whereby we perceive that the ultimate figure in mathematics is a triangle54; for there, too, there will be a stop.55 But the term perception applies in a fuller sense to mathematical intuition than to Prudence; the practical intuition of the latter belongs to a different species.5657 9. We ought also to ascertain the nature of Deliberative Excellence, and to discover whether it is a species of Knowledge, or of Opinion, or skill in Conjecture, or something different from these in kind.  Now it is not Knowledge: for men do not investigate matters about which they know, whereas Deliberative Excellence is one form of deliberation, and deliberating implies investigating and calculating. But deliberation is not the same as investigation: it is the investigation of a particular subject.58 Nor yet is it skill in Conjecture: for this operates without conscious calculation, and rapidly, whereas deliberating takes a long time, and there is a proverb that execution should be swift but deliberation slow.  Again, Deliberative Excellence is not the same as Quickness of mind,59 which is a form of skill in Conjecture. Nor yet is Deliberative Excellence any form of Opinion. But inasmuch as a bad deliberator makes mistakes and a good deliberator deliberates correctly,60 it is clear that Deliberative Excellence is some form of correctness; though it is not correctness of Knowledge, nor of Opinion. Correctness cannot be predicated of Knowledge,61 any more than can error, and correctness of Opinion is truth; and also any matter about which one has an opinion has been settled already; [then again Deliberative Excellence necessarily involves conscious calculation. It remains therefore that Deliberative Excellence is correctness in thinking, for thought has not reached the stage of affirmation;]62 for Opinion has passed beyond the stage of investigation and is a form of affirmation, whereas a man deliberating, whether he deliberates well or badly, is investigating and calculating something.  But Deliberative Excellence is a form of correctness in deliberation [so that we have first to investigate what deliberation is, and what object it deals with].63 However, ‘correctness’ in this connection is ambiguous, and plainly it is not every kind of correctness in deliberation that constitutes Deliberative Excellence. A man of deficient self-restraint or a bad man may as a result of calculation arrive at the object he proposes as the right thing to do, so that he will have deliberated correctly, although he will have gained something extremely evil; whereas to have deliberated well is felt to be a good thing. Therefore it is this kind of correctness in deliberation that is Deliberative Excellence, namely being correct in the sense of arriving at something good.64  But it is possible to arrive at a good conclusion, as well as at a bad one, by a false process of reasoning; one may arrive at what is the right thing to do, but not arrive at it on the right grounds, but by means of a wrong middle term. This quality then, which leads one to arrive at the right conclusion, but not on the right grounds, is still not Deliberative Excellence.  Again, one man may arrive at the right conclusion by prolonged deliberation, while another may do so quickly. The former case also then does not amount to Deliberative Excellence; this is correctness of deliberation as regards what is advantageous, arriving at the right conclusion on the right grounds at the right time.65  Again, a man can be said to have deliberated well66 either generally, or in reference to a particular end. Deliberative Excellence in general is therefore that which leads to correct results with reference to the end in general, while correctness of deliberation with a view to some particular end is Deliberative Excellence of some special kind. If therefore to have deliberated well is a characteristic of prudent men, Deliberative Excellence must be correctness of deliberation with regard to what is expedient as a means to the end, a true conception of which67 constitutes Prudence.10. Understanding, or Good Understanding, the quality in virtue of which we call men ‘persons of understanding’ or ‘of good understanding,’ is not the same thing as Scientific Knowledge in general （nor yet is it the same as Opinion, for in that case everybody would have understanding）, nor is it any one of the particular sciences, as medicine is the science of what pertains to health and geometry the science concerned with magnitudes.  For Understanding does not deal with the things that exist for ever and are immutable, nor yet with all of the things that come into existence, but with those about which one may be in doubt and may deliberate. Hence it is concerned with the same objects as Prudence. Understanding is not however the same thing as Prudence; for Prudence issues commands, since its end is a statement of what we ought to do or not to do, whereas Understanding merely makes judgements. （For Understanding is the same as Good Understanding; a ‘man of understanding’ means a man of good understanding.）68  Thus Understanding does not mean either the possession or the acquisition of Prudence; but when we employ the faculty of Opinion to judge what another person says about matters that are in the sphere of Prudence, we are said to understand （that is, to judge rightly for right judgement is the same as good understanding）, in the same way as learning a thing is termed understanding it when we are employing the faculty of Scientific Knowledge.  In fact, the use of the term Understanding to denote the quality that makes men ‘persons of good understanding’ is derived from understanding as shown in learning; in fact we often use ‘to learn’ in the sense of ‘to understand.’69 11. The quality termed Consideration,70 in virtue of which men are said to be considerate, or to show consideration for others （forgiveness）, is the faculty of judging correctly what is equitable. This is indicated by our saying that the equitable man is specially considerate for others （forgiving）, and that it is equitable to show consideration for others （forgiveness） in certain cases; but consideration for others is that consideration which judges rightly what is equitable, judging rightly meaning judging what is truly equitable.  All these qualities, it is reasonable to say, refer to the same thing; indeed we attribute Considerateness, Understanding, Prudence, and Intelligence to the same persons when we say of people that they ‘are old enough to show consideration and intelligence,’71 and are prudent and understanding persons. For all these faculties deal with ultimate and particular things; and a man has understanding and is considerate, or considerate for others, when he is a good judge of the matters in regard to which Prudence is displayed72; because equitable actions are common to all good men73 in their behavior towards others,  while on the other hand all matters of conduct belong to the class of particular and ultimate things （since the prudent man admittedly has to take cognizance of these things）, and Understanding and Consideration deal with matters of conduct, which are ultimate.  Also Intelligence apprehends the ultimates in both aspects—since ultimates as well as primary definitions74 are grasped by Intelligence and not reached by reasoning: in demonstrations, Intelligence apprehends the immutable and primary definitions, in practical inferences,75 it apprehends the ultimate and contingent fact, and the minor, premise, since these are the first principles from which the end is inferred, as general rules are based on particular cases; hence we must have perception of particulars, and this immediate perception is Intelligence.76  This is why it is thought that these qualities are a natural gift, and that a man is considerate, understanding and intelligent by nature, though no one is a wise man by nature.  That this is so is indicated by our thinking of them as going with certain ages: we say that at such and such an age a man must have got intelligence and considerateness, which implies that they come by nature. [Hence Intelligence is both a beginning and an end, for these things are both the starting-point and the subject matter of demonstration.]77 Consequently the unproved assertions and opinions of experienced and elderly people, or of prudent men,78 are as much deserving of attention as those which they support by proof; for experience has given them an eye for things, and so they see correctly.  We have now discussed the nature and respective spheres of Prudence and Wisdom, and have shown that each is the virtue of a different part of the soul.12. But the further question may be raised, What is the use of these intellectual virtues? Wisdom does not consider the means to human happiness at all, for it does not ask how anything comes into existence. Prudence, it must be granted, does do this; but what do we need it for? seeing that it studies that which is just and noble and good for man, but these are the things that a good man does by nature. Knowing about them does not make us any more capable of doing them, since the virtues are qualities of character; just as is the case with the knowledge of what is healthy and vigorous—using these words to mean not productive of health and vigor but resulting from them: we are not rendered any more capable of healthy and vigorous action by knowing the science of medicine or of physical training.  If on the other hand we are to say that Prudence is useful not in helping us to act virtuously but in helping us to become virtuous, then it is of no use to those who are virtuous already. Nor is it of any use either to those who are not, since we may just as well take the advice of others who possess Prudence as possess Prudence ourselves. We may be content to do as we do in regard to our health; we want to be healthy, yet we do not learn medicine.  Moreover it would seem strange if Prudence, which is inferior to Wisdom, is nevertheless to have greater authority than Wisdom: yet the faculty that creates a thing79 governs and gives orders to it. Let us now therefore discuss these difficulties, which so far have only been stated.  First then let us assert that Wisdom and Prudence, being as they are the virtues of the two parts of the intellect respectively, are necessarily desirable in themselves, even if neither produces any effect.  Secondly, they do in fact produce an effect: Wisdom produces Happiness, not in the sense in which medicine produces health, but in the sense in which healthiness is the cause of health. For Wisdom is a part of Virtue as a whole, and therefore by its possession, or rather by its exercise, renders a man happy.  Also Prudence as well as Moral Virtue determines the complete performance of man's proper function: Virtue ensures the rightness of the end we aim at, Prudence ensures the rightness of the means we adopt to gain that end. （The fourth part80 of the soul on the other hand, the nutritive faculty, has no virtue contributing to the proper function of man, since it has no power to act or not to act.81）  But we must go a little deeper into the objection that Prudence does not render men more capable of performing noble and just actions. Let us start with the following consideration. As some people, we maintain, perform just acts and yet are not just men （for instance, those who do what the law enjoins but do it unwillingly, or in ignorance, or for some ulterior object, and not for the sake of the actions themselves, although they are as a matter of fact doing what they ought to do and all that a good man should）, on the other hand it appears, there is a state of mind in which a man may do these various acts with the result that he really is a good man: I mean when he does them from choice, and for the sake of the acts themselves.  Now rightness in our choice of an end is secured by Virtue82; but to do the actions that must in the nature of things be done in order to attain the end we have chosen, is not a matter for Virtue but for a different faculty. We must dwell on this point to make it more clear.  There is a certain faculty called Cleverness, which is the capacity for doing the things aforesaid that conduce to the aim we propose, and so attaining that aim. If the aim is noble, this is a praiseworthy faculty: if base, it is mere knavery; this is how we come to speak of both prudent men and knaves as clever.  Now this faculty is not identical with Prudence, but Prudence implies it. But that eye of the soul of which we spoke83 cannot acquire the quality of Prudence without possessing Virtue. This we have said before, and it is manifestly true. For deductive inferences about matters of conduct always have a major premise of the form ‘Since the End or Supreme Good is so and so’ （whatever it may be, since we may take it as anything we like for the sake of the argument）; but the Supreme Good only appears good to the good man: vice perverts the mind and causes it to hold false views about the first principles of conduct. Hence it is clear that we cannot be prudent without being good. 13. We have therefore also to reconsider the nature of Virtue. The fact is that the case of Virtue is closely analogous to that of Prudence in relation to Cleverness. Prudence and Cleverness are not the same, but they are similar; and natural virtue is related in the same way to Virtue in the true sense. All are agreed that the various moral qualities are in a sense bestowed by nature: we are just, and capable of temperance, and brave, and possessed of the other virtues from the moment of our birth. But nevertheless we expect to find that true goodness is something different, and that the virtues in the true sense come to belong to us in another way. For even children and wild animals possess the natural dispositions, yet without Intelligence these may manifestly be harmful. This at all events appears to be a matter of observation, that just as a man of powerful frame who has lost his sight meets with heavy falls when he moves about, because he cannot see, so it also happens in the moral sphere;  whereas if a man of good natural disposition acquires Intelligence,84 then he excels in conduct, and the disposition which previously only resembled Virtue will now be Virtue in the true sense. Hence just as with the faculty of forming opinions85 there are two qualities, Cleverness and Prudence, so also in the moral part of the soul there are two qualities, natural virtue and true Virtue; and true Virtue cannot exist without Prudence.  Hence some people maintain that all the virtues are forms of Prudence; and Socrates' line of enquiry was right in one way though wrong in another; he was mistaken in thinking that all the virtues are forms of Prudence, but right in saying that they cannot exist without Prudence.  A proof of this is that everyone, even at the present day, in defining Virtue, after saying what disposition it is86 and specifying the things with which it is concerned, adds that it is a disposition determined by the right principle; and the right principle is the principle determined by Prudence. It appears therefore that everybody in some sense, divines that Virtue is a disposition of this nature, namely regulated by Prudence.  This formula however requires a slight modification. Virtue is not merely a disposition conforming to right principle, but one cooperating with right principle; and Prudence is right principle87 in matters of conduct. Socrates then thought that the virtues are principles, for he said that they are all of them forms of knowledge. We on the other hand say that the virtues cooperate with principle.  These considerations therefore show that it is not possible to be good in the true sense without Prudence, nor to be prudent without Moral Virtue. （Moreover, this might supply an answer to the dialectical argument that might be put forward to prove that the virtues can exist in isolation from each other, on the ground that the same man does not possess the greatest natural capacity for all of them, so that he may have already attained one when he has not yet attained another. In regard to the natural virtues this is possible; but it is not possible in regard to those virtues which entitle a man to be called good without qualification. For if a man have the one virtue of Prudence he will also have all the Moral Virtues together with it.）  It is therefore clear88 that, even if Prudence had no bearing on conduct, it would still be needed, because it is the virtue of89 that part of the intellect to which it belongs; and also that our choice of actions will not be right without Prudence any more than without Moral Virtue, since, while Moral Virtue enables us to achieve90 the end, Prudence makes us adopt the right means to the end.  But nevertheless it is not really the case that Prudence is in authority91 over Wisdom, or over the higher part of the intellect, any more than medical science is in authority over health. Medical science does not control health, but studies how to procure it; hence it issues orders in the interests of health, but not to health. And again, one might as well say that Political Science governs the gods, because it gives orders about everything92 in the State.