Now to speak thus is true enough but conveys no very definite meaning: as, in fact, in all other pursuits requiring attention and diligence on which skill and science are brought to bear; it is quite true of course to say that men are neither to labour nor relax too much or too little, but in moderation, and as Right Reason directs; yet if this were all a man had he would not be greatly the wiser; as, for instance, if in answer to the question, what are proper applications to the body, he were to be told, “Oh! of course, whatever the science of medicine, and in such manner as the physician, directs.” And so in respect of the mental states it is requisite not merely that this should be true which has been already stated, but further that it should be expressly laid down what Right Reason is, and what is the definition of it. Chapter II. Now in our division of the Excellences of the Soul, we said there were two classes, the Moral and the Intellectual: the former we have already gone through; and we will now proceed to speak of the others, premising a few words respecting the Soul itself. It was stated before, you will remember, that the Soul consists of two parts, the Rational, and Irrational: we must now make a similar division of the Rational. Let it be understood then that there are two parts of the Soul possessed of Reason; one whereby we realise those existences whose causes cannot be otherwise than they are, and one whereby we realise those which can be otherwise than they are,[2] (for there must be, answering to things generically different, generically different parts of the soul naturally adapted to each, since these parts of the soul possess their knowledge in virtue of a certain resemblance and appropriateness in themselves to the objects of which they are percipients);[3] and let us name the former, “that which is apt to know,” the latter, “that which is apt to calculate” (because deliberating and calculating are the same, and no one ever deliberates about things which cannot be otherwise than they are: and so the Calculative will be one part of the Rational faculty of the soul). We must discover, then, which is the best state of each of these, because that will be the Excellence of each; and this again is relative to the work each has to do.[4] There are in the Soul three functions on which depend moral action and truth; Sense, Intellect, Appetition, whether vague Desire or definite Will. Now of these Sense is the originating cause of no moral action, as is seen from the fact that brutes have Sense but are in no way partakers of moral action.[5]