Essays on the Principles of Morality and Natural Religion

Essay II. External Senses

149 u essay ii u External Senses An internal sense informs us of things passing within the mind, inclining, resolving, willing, reflecting, &c. By several external senses we discover things external. The latter is our present theme, asfaras maytendtoenforce the proof of a Deity. For the sake of perspicuity, this Essay is divided into several sections. First, perceptions of the different external senses. Second, substance and qualities. Third, primary and secondary qualities. Fourth, veracity of the external senses.i section i Perceptions of External Sense ii The perceptions of the external senses differ widely one from another. I begin with the perceptions of touch and sight as the simplest. I close my eyes and lay a hand on my writing desk. I feel my hand resisted by a hard smooth body, of a certain figure. Viewing the same desk with my eyes, the figure appears the same, as far as the perceptions of these two senses correspond . But it is more material to be observed, that by each of these senses I am informed, that the desk exists independentof me,havingcertainproperties or qualities equally independent. These senses serve evidently to inform me of things as they really exist. The senses of hearing, smelling, and tasting, raise perceptions differing widely from these mentioned. A sound is produced in me by a certain vibration of the air striking the drum of my ear: a smell, by effluvia touching 150 external senses my nostrils: and a taste by a bit of matter touching my palate. With respect to these senses, it is not a little remarkable, that their perceptions have no resemblance to the causes that produced them; nor do they correspond to any thing existing independent of me. The beat of a drum produces nothing but a vibrating motion in the air; nor does any thing touch my ear but that vibration. The effect however is a perception of sound, which has not the slightest affinity either to the beat of the drum or vibration of the air; nor has it any existence but in my mind. A rose emits effluvia which touch my nostrils: the smell I perceive is neither in the rose nor in the effluvia. The sweetness I taste in sugar, is produced by the sugar; but in vain would one search for that quality in the sugar, more thaninany otherbitof matter. From this analysis it appears, that a sound, a smell, a taste, are not matter nor qualities of matter; but effects produced in a percipient. No mortal would without experience imagine, that such marvelous effects could be produced by causes in all appearance so inadequate, effects however that contribute in a high degree to our well-being. section ii Substance and Quality As a just conception of the terms substance and quality is necessary in many branches of reasoning, particularly in reasoning about a Deity, and as the explanation given of these terms by Mr. Locke, our great master in logic, is extremely obscure, I shall endeavour to ascertain their meaning, to the satisfaction, I expect, of my reader.1 I cast my eye upon a tree, and perceive figure, extension, colour, and sometimes motion. Were these perceived as separate objects without relation to any other thing, I should never have any idea of substance. This possibly may be the condition of some animals; but the eye of man is more perfect. What we really perceive, is a tree of a certain figure,size,andcolour. When I see motion, my perception is not of motion separately, but of a body moving. And so closely are these united, that we cannot even form a 1. See “Of Our Complex Ideas of Substances,” in Locke, Essay, II.xxiii. external senses 151 conception of motion, nor of colour, nor of figure, as independent existences , but as belonging to the tree and inhering in it. In short, the sense of seeing is given us to perceive things as they really exist; and did it not make us acquainted with things as they exist, we would be ill qualified for living in this world. Now, when we abstract from particulars, and reason in general, the things that have not a separate existence are termedqualities, and the thing they belong to, body or substance. Thus the ideaof substance, as well as of qualities, is derived from sight. And the object so qualified, is at the same...