MENTAL PHILOSOPHY.

PART FIRST.

PHILOSOPHY OF SENSATIONS.

CHAPTER I.

GENERIC PROPERTIES OF SENSATIONS, EMBRACING THEIR NATURE, ORIGIN AND OFFICE.

§ 1. SENSATIONS are states of mind which result immediately from peculiar conditions of the body. Weariness, fatigue, heat and cold, and sensations of touch and sight, are of this description. Sensations occur by means of bodily organs, and are distributed into several different classes, as follows: 1. Sensations which are the basis of the appetites; 2. Weariness and fatigue; 3. Heat and cold; 4. Pain; 5. Touch; 6. Sight; 7. Hearing; 8. Taste; 9. Smell.

Sensations all agree in being effects produced directly on the mind by peculiar states of the body; and the states of the body on which they depend, are themselves effects of other causes, many of which are external to the body. Sensations are so many modes of action by which material objects affect the mind, and so many mediums of communication between mind and matter. Matter is discerned only through the medium of sensations; and its primary properties considered with respect to minds, are its powers of affecting them with sensations. Considered with respect to their principal use, sensations may be divided into two classes: 1. Those which are subservient to the preservation of life and health; and 2. Those which are subservient to the acquisition of a knowledge of external objects. The sensations subservient to the preservation of life and health, are hunger and thirst, weariness and fatigue, and heat and

cold. Those which are subservient to the acquisition of a knowledge of external objects, are touch, sight, hearing, taste, and smell.

2. To the question; What are sensations? The answer is, sensations are peculiar states of mind, dependent on peculiar conditions of the body. These states differ from each other in several respects, and can be known only by experience. Some of them are pleasurable, some painful, and some indifferent. Colors are experienced by the eye, sounds by the ear, and resistances by touch. But what are the colors, sounds, and resistances, which are thus experienced? Are they things out of the mind or in it? Have they any existence where there are no minds to appreciate them? Or are they effects produced on the mind, and which have no existence any farther than they are experienced? The latter is undoubtedly the fact. Color is in the mind, sound is in the mind, touch, and other sensations are in the mind. They are produced there however, by external objects, and are constantly referred to those objects as their causes, in all rational estimates of them. A colored object is an object which produces the sensation of color, a resisting object, one which produces sensations of resistance, and a sounding body is a body which produces sensations of sound.

§ 3. Words are applied to denote sensations in a perfectly arbitrary manner, and derive their whole significancy from the general agreement of mankind. They express simply the ideas of men in respect to sensations, just as other words express their ideas in respect to the motions, sizes, and forms of bodies. Those sensations, however, which are designed to make us acquainted with external objects, are seldom objects of thought, except to philosophers. The mind experiences the sensation of color, and directs its attention not to the sensation, but to the colored object, and employs its reasoning almost exclusively on that; it experiences the sensation of sound, and thinks usually of the sounding body, associating the sensation intimately with it; or in the case of music and vocal language, it is not the sounding body which is the principal object of thought, but the ideas and sentiments, of which sounds are the constituted symbols.

§ 4. Sensations are ultimate facts in human experience, and the first objects of knowledge. One sensation may be distinguished from another, and one class of sensations from

other classes, and complex sensations may be resolved into simple ones; but simple sensations are ultimate objects of thought, and ultimate facts in experience, which can be known only by being felt, and which can be described only by being referred to their appropriate agents, organs, objects, and uses. To understand colors, we must see; to understand sounds, we must hear; and to understand the other sensations, we must experience them. But having had experience of any class of sensations in some degree, we may attain ideas of other classes and other varieties of them, by reasoning.

The different classes of sensations form one beautiful and harmonious system of things, to be observed, considered and reasoned from. With them, knowledge, not opinion, merely commences. We feel pain, henceforth pain becomes a fact in our experience, and an object of our knowledge. We know both that there is such a thing, and that we have felt it, and may feel it again. We experience the sensations of color, and henceforth understand that there are such things as colors. So of all the other sensations. In reasoning from our sensations we may fall into errors; but the sensations themselves, from which our reasoning commences, are matters of the utmost certainty.

§ 5. How the mind is affected in sensations, or what the nature of the mind is, other than that of a being capable of sensations and ideas, it does not fall within the purpose of this chapter to inquire, and it may not be possible fully to determine. We confine our views for the present, to sensations considered simply as ultimate facts in the experience of sentient beings, and as certain states of the mind.

The first sensation in the experience of a sentient being, is the commencement of intellectual life. With it consciousness begins; and from it the acquisition of knowledge and the play of imagination commences. Sensation after sensation follows, drawing after it thought after thought; and introducing the rational mind to a knowledge of itself and of the external world; and launching it forth on broad oceans of experiment in the pursuit of boundless good.

§ 6. Sensations may be considered as possessing quality and quantity. The quality of sensations is that which is peculiar to them as a generic class of mental phenomena; and which distinguishes each class of sensations from others. It is therefore incapable of definition, and can only be de

scribed by those terms which describe sensations as a distinct class of phenomena. In respect to quality, however, sensations admit of being distributed into three classes; Pleasing, Painful, and Indifferent; examples of which may be multiplied indefinitely. We no sooner experience sensations than we begin to reason from them to their causes, and to form ideas of external objects, and estimate those objects according to the sensations which they produce. The quality of the sensations which we derive from material objects is the primary ground of the estimates which we form respecting them. From touch we form ideas of objects as tangible; from sound, as audible; from sight, as visible and colored.

So we estimate objects of pleasing sensations as pleasing; those of painful sensations as painful; and those of sensations which are indifferent, as indifferent. The sensible qualities of objects are all relative to the capacities of sensation, according to which they are estimated. That which produces the sensation of sweetness is sweet, and that which produces the opposite sensation of bitterness, is bitter; and as far as the capacities of sensation in different persons, differ, objects to them, will be relatively different. It is on this account that many articles of food which are agreeable to some, are disagreeable to others. The articles are essentially the same, but relatively different. The general agreement of mankind in their estimates of sensible objects, depends on the possession of similar capacities of sensation. As a general rule, men are similarly affected by similar objects. What is colored to one, is colored to all; what is sweet to one, is sweet to all; and what is resisting to one, is resisting to all.

§ 7. The quantity of sensations may be resolved into two elements, time and intensity. All sensations occupy time, and their quantity, other things being equal, is proportionable to the times during which they continue.

The intensity of sensations is a quality independent of time, and dependent on other appropriate conditions. It denotes the quantity of sensations considered with respect to given times, or without respect to time. The amount of pain which we experience is in proportion to its intensity and time; and pains may differ in intensity from those which are the slightest that can be felt, to such as are too

great to be endured for any considerable time without overpowering the vital system.

§ 8. The nature of sensations as effects of certain causes, is one of their distinguishing properties, and one that is early observed by every sentient being. It is by this means that sensations become the signs of things, and answer their great purpose as conditions and means of knowledge. Sensations do not occur in all cases necessarily as the effect of organic conditions adapted to produce them. Visible objects may be before the eye, and not be seen; sounds may vibrate upon the ear, and not be heard; and the conditions of pain may exist in the different organs of the body, and pain not be felt. This often occurs when the mind is intensely engaged in other exercises, and also in sleep. Hence the use of diversion and business to allay pain, and induce an insensibility to painful objects. Hence, too, the greater intensity both of the pains and pleasures of sense when we make them the exclusive objects of our attention. We infer, therefore, that attention is to a great extent one of the conditions of sensation; and that the appropriate mastery of the mind over this class of its phenomena, is exercised to a great extent through the medium of attention.

Those who are most disengaged from other mental exercises, and who attend most to the sensations which they experience, other things being equal, experience from given objects sensations of the greatest intensity; and in proportion as the mind is engaged in other exercises, its capacities of sensation are for the time impaired or entirely suspended.

§ 9. The capacities of sensation admit of different degrees of susceptibility. Different persons possess constitutional differences in this respect; and the susceptibilities of the same persons are different in different states of health and sickness, and in different stages of life.

Those whose susceptibilities are greatest, other circumstances being equal, experience sensations of the greatest intensity from given objects; and some are the subjects of sensations of the greatest intensity in circumstances and from objects which do not excite the sensibilities of others at all.

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§ 10. Sensations occur by means of organs. The eye an organ of sight, the ear of hearing, the mouth of taste,