For how could it possibly be, that a man should be better and worse than himself, and at once both his own master and slave, if every one were not in some sort naturally double or twofold, having in himself at the same time a better part and a worse? For so may he be reckoned to have a power over himself and to be better than himself, who has his worse and inferior faculties in obedience and subjection to the superior and more excellent; whereas he who suffers his nobler powers to fall under the government and direction of the intemperate and irrational part of the soul is less and worse than himself, and has wholly lost the command over himself, and is in a state which is contrary to Nature. For by the order of Nature, reason, which is divine, ought to have the sovereignty and dominion over the irrational and brutal faculties, which, deriving their original from the body, and being incorporated, as it were, and thoroughly mixed therewith, bear a very near resemblance to it, are replenished with, and do participate in common of the qualities, properties, and passions thereof; as is plain from our more vehement motions and efforts towards corporeal objects, which always increase or diminish in vigor according to the several changes and alterations which happen in the body. From whence it is that young men are in their lusts and appetites, because of the abundance and warmth of their blood, so quick, forward, hot, and furious; whereas in old men all natural fire being almost extinguished, and the first principles and source of the affections and passions, seated about the liver, being much lessened and debilitated, reason becomes more vigorous and predominant, while the appetites languish and decay together with the body. And after this manner it is that the nature of beasts is framed and disposed to divers passions. For it is not from any strength or weakness of thought, or from any opinions right or wrong which they form to themselves, that some of them are so bold and venturous, and dare encounter any thing, and others of them are fearful and cowardly, shrinking at every danger; but from the force and power of the blood, the spirits, and the body does this diversity of passions in them arise; for that part where the passions are seated, being derived from the body, as from its root, retains all the qualities and propensions of that from whence it is extracted. Now that in man there is a sympathy and an agreeable and correspondent motion of the body with the passions and appetites, is proved by the paleness and blushings of the face, by the tremblings of the joints, and by the palpitation of the heart; and, on the contrary, by the diffusion or dilatation which we feel upon the hope and expectation of pleasures. But when the mind or intellect doth move of itself alone, without any passion to disorder and ruffle it, then is the body at repose and rests quiet, having nothing at all to do with those acts and operations of the mind; as, when it takes into consideration a proposition in mathematics or some such scientifical thing, it calls not for the aid or assistance of the irrational or brutal faculties. From whence also it is very apparent that there are in us two distinct parts, differing in their powers and faculties from one another.