The first difference is the ability to act from a distance. Certainly, touch also may in some manner perceive the presence or absence of the sun, by means of the impressions of heat and cold; and in like manner the presence or absence, and the more or less close proximity of some bodies, etc.; but not only are these impressions far from having the same variety and rapidity as those of hearing, but they would not even give us any idea of distance, if we had not already perceived it otherwise than by touch. Heat and cold, dryness and moistness, are what the impressions which some bodies, though distant, may make upon touch are reduced to; and these impressions are clearly of a nature to be exposed to many serious errors. 62. If we suppose a man, having only the sense of touch, to know the presence or absence of the sun above the horizon, his only rule being the temperature of the atmosphere, which depends upon a thousand causes having no connection with the orb of day, it will happen that the natural or artificial change of it will lead him into error. The dampness which we perceive around a lake is a sign of the nearness of the water; but do we not a thousand times experience the feeling of dampness from causes operating on the atmosphere, altogether independent of the waters of a lake? It is certain that the concentration of all sensitive forces upon one sense, the absence of all distraction, and continual attention to only one kind of sensations, might raise the delicacy of touch to a degree of perfection which we probably do not know; just as the habit of connecting ideas with respect to only one order of sensations, and of forming judgments concerning them, produces a precision, exactness, and variety, far superior to all that we can imagine. But however far we might extend our conjectures upon this head, it is certain that there is a limit in the nature of the organ and of its relations to bodies. This organ must be limited to contiguous objects, in order to receive well determined impressions; and with respect to those that are distant, and can act upon it, they can do this by causing on it an impression such as the nature of both permits, heat or cold, dryness or dampness, and if you will, a certain pressure either greater or less. So far as a great many other objects are concerned, we cannot imagine any action. However much the circle of this class of sensations be enlarged, it must ever be very limited. Moreover, we must observe, that the perfectibility of touch by means of its isolation does not belong to it exclusively, but extends likewise to the other senses; for it is founded on the laws of organization, and the generation of our ideas. 63. To comprehend the superiority of hearing to touch in this matter, we have only to consider the relation of distances, the variety of objects, the rapidity of the succession of sensations, the simultaneousness so much greater in hearing than in touch, and their relations to speech.