Since then the object of the present treatise is not mere speculation, as it is of some others (for we are enquiring not merely that we may know what virtue is but that we may become virtuous, else it would have been useless), we must consider as to the particular actions how we are to do them, because, as we have just said, the quality of the habits that shall be formed depends on these. Now, that we are to act in accordance with Right Reason is a general maxim, and may for the present be taken for granted: we will speak of it hereafter, and say both what Right Reason is, and what are its relations to the other virtues.[4] But let this point be first thoroughly understood between us, that all which can be said on moral action must be said in outline, as it were, and not exactly: for as we remarked at the commencement, such reasoning only must be required as the nature of the subject-matter admits of, and matters of moral action and expediency have no fixedness any more than matters of health. And if the subject in its general maxims is such, still less in its application to particular cases is exactness attainable:[5] because these fall not under any art or system of rules, but it must be left in each instance to the individual agents to look to the exigencies of the particular case, as it is in the art of healing, or that of navigating a ship. Still, though the present subject is confessedly such, we must try and do what we can for it. First then this must be noted, that it is the nature of such things to be spoiled by defect and excess; as we see in the case of health and strength (since for the illustration of things which cannot be seen we must use those that can), for excessive training impairs the strength as well as deficient: meat and drink, in like manner, in too great or too small quantities, impair the health: while in due proportion they cause, increase, and preserve it. Thus it is therefore with the habits of perfected Self-Mastery and Courage and the rest of the Virtues: for the man who flies from and fears all things, and never stands up against anything, comes to be a coward; and he who fears nothing, but goes at everything, comes to be rash. In like manner too, he that tastes of every pleasure and abstains from none comes to lose all self-control; while he who avoids all, as do the dull and clownish, comes as it were to lose his faculties of perception: that is to say, the habits of perfected Self-Mastery and Courage are spoiled by the excess and defect, but by the mean state are preserved.