Sense sees only the outside of things, reason acquaints itself with their natures.—Sensation is only a mode of feeling in the mind; but knowledge implies an active and vital energy of the mind. Feeling pain, for example, is the effect of sense; but the understanding is employed when pain itself is made an object of the mind's reflexion, or held up before it, in order to discover its nature and causes. Mere sense can perceive nothing in the most exquisite work of art; suppose a plant, or the body of an animal; but what is painted in the eye, or what might be described on paper. It is the intellect that must perceive in it order and proportion; variety and regularity; design, connection, art, and power; aptitudes, dependencies, correspondencies, and adjustment of parts, so as to subserve an end, and compose one perfect whole; things which can never be represented on a sensible organ, and the ideas of which cannot be passively communicated, or stamped on the mind by the operation of external objects.--Sense cannot perceive any of the modes of thinking beings; these can be discovered only by the mind's survey of itself.
Richard Price, A Review of the Principal Questions and Difficulties in Morals, pp. 20-22.