material mind itself, by which, in its relation to the structure of the human frame, it is rendered more liable to one particular state than to another. From any one, therefore, of these several causes, or even from a co-operation of two or more of them, there may, in the same person, be an innate tendency to receive a more vivid degree of pleasure from sound than from colour; or a degree of vividness, no less disproportionate, may be imparted to the sensations connected with the gustatory organs. Even with regard to feelings of the same kind, a variety of predilections may subsist. One tint of colour or shade may naturally give more delight than another, and the same observation may apply to particular odours, tones, &c. Lastly, this constitutional variety of susceptibilities evinced in the several organs of the body, may again differ in different individuals. In the next place, when we contemplate man as a social being, we shall find, that his innate and individual susceptibilities of pleasure or of pain are liable to be still farther modified. Moral laws exist which determine on what occasions of social intercourse particular hopes and fears shall be excited. Such definite occasions are connected with the acquisition or privation of knowledge, of power, of society, of the means of evincing gratitude, of the means of resentment, and of the esteem of our fellow-creatures. These remarks lead me to attempt the explanation of a very important law, relative to the manner in which the mind may be influenced. A morbific cause, whether pleasurable or painful, can only co-operate with moral agents endowed with a similar specific power. Thus, if we allow the nitrous oxide to be a morbific cause, (which the utmost range of its action certainly shews,*) it does nothing more than single out, as it were, all sensations and ideas which are of themselves morally pleasurable, but has no immediate effect on the painful feelings with which they are naturally mingled. For this reason, it is easy to suppose, that when Sir Humphrey Davy imbibed a large quantity of the gas, all the ideas connected with his favourite chemical researches would be among the first to be affected by this powerful agent. And, accordingly, on one occasion, he remarks, "I gradually began to lose the perception of external things, and a vivid and intense recollection of some former experiments passed through the mind." Again, in the opposite effects arising from the febrile miasma, this powerful agent imparts no additional degree of vividness to the quality of any feelings, but such as, from the previous operation of moral agents, are, of themselves, painful. The action of various other morbific causes admits of a similar explanation. 66 *Orfila, in his history of poisons, remarks, that the nitrous oxide dissolves with great promptitude in the veins of animals into which it is injected, but produces no apparent change in the arterial blood. When gradually injected, it does not at first give rise to any observable effect; but if the injections are multiplied, they are followed by phenomena, like those attending copious inhalations, and to these death may supervene, which (as he supposes) begins by the brain. If injected in a large quantity at once, it occasions the distension of the pulmonary portion of the heart, and is likewise fatal. In contemplating, then, the co-operation of morbific causes with moral agents, there must evidently subsist two varieties of ecstacy. One variety of ecstacy must occur when the cause of mental excitement, to which the affection is referable, has added to the vividness of pleasurable feelings, but has proportionally diminished that of painful feelings. Another, and a second variety of ecstacy must occur, when the cause of mental excitement, to which the affection is referable, has added to the intensity of painful feelings, but has proportionally diminished the vividness of pleasurable feelings. These two varieties of ecstacy will be constantly kept in view in the ensuing chapters. CHAPTER X. THE FREQUENT EFFECT OF GENERAL MORBIFIC EXCITEMENTS IN RENDERING THE MIND UNCONSCIOUS EITHER OF PLEASURABLE OR PAINFUL FEELINGS. "What is mortal man? So changeable his being, with himself THOMPSON'S Progress of Sickness. BEFORE explaining a very important law of the mind relative to consciousness, which is materially connected with the object of the present dissertation, I shall briefly glance at the progress that has been made in the metaphysical part of this inquiry. Sensations and ideas having been considered as nothing more than states of the immaterial mind, I proceeded upon the hypothesis, that, as long as vitality subsisted, a succession of such states, even during syncope and sleep, was continually recurring. It was next shewn, that the comparative degree of vividness which subsists between sensations and ideas, suggest to the mind the intellectual feelings of the present and of the past; and, along with this relation of time, the identity of one mind, as existing in a succession of states; and that, when ideas are rendered more vivid than sensations, a revival of past feelings is contemplated as the result of actual impressions. A further observation was made, that the notion of the present and of the past, as well as of the proper identity of the mind, necessarily enters into our definition of consciousness; and that mental consciousness cannot be induced until sensations and ideas have attained a certain degree of vividness. Hence the unconsciousness attending the faint impressions of sleep. It was also pointed out, that a morbific agent capable of exciting the feelings of the mind, exerted a specific power over some particular quality of the feelings; and that it could only impart a definite addition of pleasure or pain to feelings which, from the paramount influence of moral agents, were of themselves either pleasurable or painful. The law, then, to be explained is this: When a morbific agent adds to the general vividness of our pleasurable feelings, every feeling of an opposite or painful quality is, in an inverse proportion, rendered less vivid ; and, vice versa, the same law holds good when a morbific agent adds to the vividness of all our painful feelings. It follows, then, that as consciousness is never excited until sensations and ideas have attained a certain degree of vividness, the intensity imparted to pleasurable states of the mind may be so great, that, from the extreme of faintness to which affections of an opposite quality will be proportionably reduced, every |