There are several points in this definition of the mean upon which moral virtue depends of which we must take note unless we are to misunderstand Aristotle seriously. To begin with, the definition expressly says that "moral goodness is a state of will or choice." Thus it is not enough that one should follow the rule of the mean outwardly in one’s actions; one’s personal will must be regulated by it. Goodness of character is inward; it is not merely outward. Next we must not suppose that Aristotle means that the "just enough" is the same for all our feelings, that every impulse has a moral right to the same authority in shaping our conduct as any other. How much or how little is the just enough in connection with a given spring of action is one of the things which the wise man’s rule has to determine, just as the wise physician’s rule may determine that a very little quantity is the just enough in the case of some articles of diet or curative drugs, while in the case of others the just enough may be a considerable amount. Also the right mean is not the same for every one. What we have to attain is the mean relatively to _ourselves_, and this will be different for persons of different constitutions and in different conditions. It is this relativity of the just enough to the individual’s personality and circumstances which makes it impossible to lay down precise rules of conduct applicable alike to everybody, and renders the practical attainment of goodness so hard. It is my duty to spend some part of my income in buying books on philosophy, but no general rule will tell me what percentage of my income is the right amount for me to spend in this way. That depends on a host of considerations, such as the excess of my income above my necessary expenses and the like. Or again, the just enough may vary with the same man according to the circumstances of the particular case. No rule of thumb application of a formula will decide such problems. Hence Aristotle insists that the right mean in the individual case has always to be determined by immediate insight. This is precisely why goodness of intellect needs to be added to goodness of character. His meaning is well brought out by an illustration which I borrow from Professor Burnet. "On a given occasion there will be a temperature which is just right for my morning bath. If the bath is hotter than this, it will be too hot; if it is colder, it will be too cold. But as this just right temperature varies with the condition of my body, it cannot be ascertained by simply using a thermometer. If I am in good general health I shall, however, know by the feel of the water when the temperature is right. So if I am in good moral health I shall know, without appealing to a formal code of maxims, what is the right degree, _e.g._ of indignation to show in a given case, how it should be shown and towards whom." Thus we see why Aristotle demands goodness of