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.

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

and the whole body of touch and pain. We often conceive of the eye as seeing, the ear as hearing, and the body as experiencing pain or pleasure. But, strictly speaking, it is the mind only, that sees, hears, tastes, and experiences pain or pleasure. One and the same mind is the subject of all these exercises, and is the sole agent for whose use all the bodily organs are constructed. The mind sees with the eye, hears with the ear, and feels pain or pleasure throughout the whole body by means of the body. Sensations in all their varieties are phenomena of minds, and relate to the mind which experiences them, as their subject, to the body and the different bodily organs, as instruments for their production, and to external objects, as their more remote conditional causes. There cannot be sensation without a mind capable of exercising it; nor, according to our present constitution, without an organ by which it may be exercised, and objects to act upon that organ. The three essential conditions of sensations, therefore, so far as the experience of man is concerned in this life, are mind, organized bodies, and an external material world. Organized bodies are organs of communication between minds and the external material world. Except through the medium of its body, each mind is an insulated being, incapable of the least communication with other minds, and of the least impression from material objects, and consequently incapable of any conscious action or state whatever; so that, as far as happiness is concerned, it might as well be annihilated or be a non-entity .The body brings the mind into intelligent correspondence with the material world, and through that with the spiritual world. For all that we feel, for all that we know, for all that we do, we are dependent on our bodies. The different parts of the body are organized in adaptation to the susceptibilities of the mind, so as to serve it and become instruments for the development of its powers and susceptibilities.

§ 11. In the interior of this complex organ dwells the mind, invisible, intangible, unapproachable. Beautiful image of God! Mysterious and wonderful agent! Who can sound thy depths? Who can scale thy heights? Who can estimate thy powers or declare thy destiny? Who can penetrate thy sanctuary, and lay his hand upon thee, and grasp thy mysterious substance? None but thy Maker can reach thee; none but he can tell the flights of fancy, the

conquests of reason, and the unfathomed depths of affection which thou art destined to accomplish and experience. Here thou sittest like a king on his throne. Thy body is thy palace; but it is not thy palace only. It is a system of engines, a collection of instruments for the reception of impressions from the external world, and for making impressions upon it; and thou sittest recipient and communicant, acted upon and acting! How has philosophy been humbled before thy majesty and thy mysteries!

§ 12. During this life all the powers of the mind are dependent on the body, and are liable to be deranged or suspended entirely, by diseases and injuries of this complex organ. When divested of bodily organs at death, the mind is thrown back upon the hands of God, to be provided for in other modes, and to be furnished with other capacities suited to the disembodied state. Death divests us of all the instrumentalities which are exercised in the phenomena of this life. It removes the organs of sensation, and annihilates the conditions on which all thought and feeling in this life depend. The instant that our souls are disengaged from the body, is that of their introduction into the world of spirits. That instant we are authorized by the Scriptures and by the principles of natural religion to believe, that they become invested with new powers analogous to those possessed in this life, but of a higher order. Reason, imagination, memory, and the affections must continue substantially the same as here; but disembodied spirits must be furnished with other capacities analogous to those of sensation, and as perfectly adapted to the disembodied state as the capacities of sensation are to the present embodied one

Relations of Sensations to Ideas.

§ 13. The relations of sensations to ideas are of great importance and ought to be carefully observed. Sensations are generally confounded with ideas, and ideas with sensations. But these two classes of phenomena are entirely distinct and different from each other. Sensations are one kind of phenomena, one kind of things, ideas are another. In all perceptions of external objects, sensations are the medium of perception. We perceive tangible objects by touch; visible objects, by sight; and invisible objects, by hearing. Touch, sight, and hearing, are in these cases the mediums of perception. So it is in all other cases.