Since we have already stated that one should rationally choose the mean, not the excess or the deficiency, and that the mean is as correct reason prescribes, let us now analyse this prescription.
In all the states of character we have mentioned, and in the others as well, there is a sort of target, and it is with his eye on this that the person with reason tightens or loosens his string. There is also a sort of standard for the mean states, which, as we say, lie between excess and deficiency and are in accordance with correct reason.
But to say this, though true, is not at all clear. For in all other practices of which there is a science it is true to say that one should exert oneself and relax neither too much nor too little, but to the extent of the mean that is prescribed by correct reason. But having grasped only this, someone would be none the wiser; for example, you would not know what sort of treatments to use on your body if someone were to say that you should employ those that medicine requires, and in the way that a medical practitioner employs them. With states of the soul as well, then, we must not only offer this truism, but also determine what correct reason is and what its standard is.
When we had classified the virtues of the soul, we said that some are virtues of character, others of thought.