Part V. Of the Power of the Understanding, or of Human Freedom. Preface At length I pass to the remaining portion of my Ethics, which is concerned with the way leading to freedom. I shall therefore treat therein of the power of the reason, showing how far the reason can control the emotions, and what is the nature of Mental Freedom or Blessedness ; we shall then be able to see, how much more powerful the wise man is than the ignorant. It is no part of my design to point out the method and means whereby the understanding may be perfected, nor to show the skill whereby the body may be so tended, as to be capable of the due performance of its functions. The latter question lies in the province of Medicine, the former in the province of Logic. Here, therefore, I repeat, I shall treat only of the power of the mind, or of reason ; and I shall mainly show the extent and nature of its dominion over the emotions, for their control and moderation. That we do not possess absolute dominion over them, I have already shown. Yet the Stoics have thought, that the emotions depended absolutely on our will, and that we could absolutely govern them. But these philosophers were compelled, by the protest of experience, not from their own principles, to confess, that no slight practice and zeal is needed to control and moderate them : and this someone endeavoured to illustrate by the example (if I remember rightly) of two dogs, the one a house-dog and the other a hunting-dog. For by long training it could be brought about, that the house-dog should become accustomed to hunt, and the hunting-dog to cease from running after hares. To this opinion Descartes not a little inclines. For he maintained, that the soul or mind is specially united to a particular part of the brain, namely, to that part called the pineal gland, by the aid of which the mind is enabled to feel all the movements which are set going in the body, and also external objects, and which the mind by a simple act of volition can put in motion in various ways. He asserted, that this gland is so suspended in the midst of the brain, that it could be moved by the slightest motion of the animal spirits : further, that this gland is suspended in the midst of the brain in as many different manners, as the animal spirits can impinge thereon ; and, again, that as many different marks are impressed on the said gland, as there are different external objects which impel the animal spirits towards it ; whence it follows, that if the will of the soul suspends the gland in a position, wherein it has already been suspended once before by the animal spirits driven in one way or another, the gland in its turn reacts on the said spirits, driving and determining them to the condition wherein they were, when repulsed before by a similar position of the gland. He further asserted, that every act of mental volition is united in nature to a certain given motion of the gland.