Consciousness is not a "principle" or substance of any kind, nor is it, strictly speaking, a property of any substance or being. It is a peculiar action of the nervous system, and the system is said to be sensible, or to possess the property of sensibility, because those sentient actions which constitute our different consciousnesses may be excited in it. The nervous system includes not only the brain and spinal marrow, but numerous soft white cords, called nerves, which extend from the brain and spinal marrow to every part of the body in which a sensation can be excited.

A sensation is a sentient action of a nerve and the brain; a thought or idea (both the same thing) is a sentient action of the brain alone. A sensation or a thought is consciousness, and there is no consciousness but that which consists either in a sensation or a thought.

Agreeable consciousness constitutes what we call happiness, and disagreeable consciousness constitutes misery. As sensations are a higher degree of consciousness than mere thought, it follows that agreeable sensations constitute a more exquisite happiness than agreeable thoughts. That portion of happiness which consists in agreeable sensations is commonly called pleasure. No thoughts are agreeable except those which were originally excited by or have been associated with agreeable sensations. Hence, if a person never had experienced any agreeable sensations, he could have no agreeable thoughts, and would, of course, be an entire stranger to happiness.

There are five species of sensations—seeing, hearing, smelling, tasting and feeling. There are many varieties of feeling—as the feelings of hunger, thirst, cold, hardness, etc. Many of these feelings are excited by agents that act upon the exterior of the body, such as solid substances of every kind, heat, and various chemical irritants. These latter feelings are called passions.

Those passions which owe their existence chiefly to the state of the brain, or to causes acting directly upon the brain, are called the moral passion. They are grief, anger, love, etc. They consist of sentient actions, which commence in the brain and extend to the nerves in the region of the stomach, etc. But when the cause of the internal feeling of passion is seated in some organ remote from the brain, as in the stomach, genital organs, etc., the sentient action which constitutes the passion commences in the nerves of such organ and extends to the brain, and the passion is called an appetite, instinct, or desire. Some of these passions are natural, as hunger, thirst, the reproductive instinct, the desire to urinate, etc. Others are gradually acquired by habit A hankering for stimulants, as spirits, opium and tobacco, is one of these.

Such is the nature of things that our most vivid and agreeable sensations cannot be excited under all circumstances, nor beyond a certain extent under any circumstances, without giving rise in one way or another to an amount of disagreeable consciousness or misery, exceeding the amount of agreeable consciousness which attends such ill-timed or excessive gratification. To excite agreeable sensations to a degree not exceeding this certain extent is temperance; to excite them beyond this extent is intemperance; not to excite them at all is mortification or abstinence. This certain extent varies with different individuals, according to their several circumstances, so that what would be temperance in one person may be intemperance in another.

To be free from disagreeable consciousness is to be in a state which, compared with a state of misery, is a happy state; yet absolute happiness does not exist in the absence of misery, if it does, rocks are happy. It consists, as aforesaid, in agreeable consciousness. That which enables a person to excite or maintain agreeable consciousness is not happiness; but the idea of having such in one's possession is agreeable, and of course is a portion of happiness. Health and wealth go far in enabling a person to excite and maintain agreeable consciousness. That which gives rise to agreeable consciousness is good, and we desire it. If we use it intemperately, such use is bad, but the thing itself is still good. Those acts (and intentions are acts of that part of man which intends) of human beings which tend to the promotion of happiness are good, but they are also called virtuous, to distinguish them from other things of the same tendency. There is nothing for the word virtue to signify, but virtuous actions. Sin signifies nothing but sinful actions, and sinful, wicked, vicious, or bad actions are those which are productive of more misery than happiness.

When an individual gratifies any of his instincts in a temperate degree, he adds an item to the sum total of human happiness, and causes the amount of human happiness to exceed the amount of misery farther than if he had not enjoyed himself, therefore it is virtuous, or, to say the least, it is not vicious or sinful for him to do so. But it must ever be remembered that this temperate degree depends on circumstances; that one person's health, pecuniary circumstances, or social relation may be such that it would cause more misery than happiness for him to do an act which being done by a person under different circumstances would cause more happiness than misery. Therefore, it would be right for the latter to perform such act, but not for the former.

Again: owing to his ignorance, a man may not be able to gratify a desire without causing misery (wherefore it would be wrong for him to do it), but with knowledge of means to prevent this misery, he may so gratify it that more pleasure than pain will be the result of the act, in which case the act, to say the least, is justifiable. Now, therefore, it is virtuous, nay, it is the duty, for him who has a knowledge of such means, to convey it to those who have it not, for by so doing he furthers the cause of human happiness.

Man by nature is endowed with the talent of devising means to remedy or prevent the evils that are liable to arise from gratifying our appetites; and it is as much the duty of the physician to inform mankind of the means to prevent the evils that are liable to arise from gratifying the productive instinct as it is to inform them how to keep clear of the gout or dyspepsia. Let not the old ascetic say we ought not to gratify our appetites any further than is necessary to maintain health and to perpetuate the species. Mankind will not so abstain, and if any means to prevent the evils that may arise from a farther gratification can be devised, they need not. Heaven has not only given us the capacity of greater enjoyment, but the talent of devising means to prevent the evils that are liable to arise therefrom, and it becomes us, "with thanksgiving," to make the most of them.

FRUITS OF PHILOSOPHY.