The Lives and Opinions of Eminent Philosophers by Diogenes Laërtius (best free ebook reader txt) 📕

retain this principle, and to know that the images have an incomparable thinness; which fact indeed is in no respect contradicted by sensible appearances. From which it follows that their rapidity also is incomparable; for they find everywhere an easy passage, and besides, their infinite smallness causes them to experience no shock, or at all events to experience but a very slight one, while an infinite multitude of elements very soon encounter some resistance.

One must not forget that the production of images is simultaneous with the thought; for from the surface of the bodies images of this kind are continually flowing off in an insensible manner indeed, because they are immediately replaced. They preserve for a long time the same disposition, and the same arrangement that the atoms do in the solid body, although, notwithstanding, their form may be sometimes altered. The direct production of images in space is equally instantaneous, because these images are only light substances destitute of depth.

But there are other manners in which natures of this kind are produced; for there is nothing in all this which at all contradicts the senses, if one only considers in what way the senses are exercised, and if one is inclined to explain the relation which is established between external objects and ourselves. Also, one must admit that something passes from external objects into us in order to produce in us sight and the knowledge of forms; for it is difficult to conceive that external objects can affect us through the medium of the air which is between us and them, or by means of rays, whatever emissions proceed from us to them, so as to give us an impression of their form and color. This phenomenon, on the contrary, is perfectly explained if we admit that certain images of the same color, of the same shape, and of a proportionate magnitude pass from these objects to us, and so arrive at being seen and comprehended. These images are animated by an exceeding rapidity, and, as on the other side, the solid object forming a compact mass, and comprising a vast quantity of atoms, emits always the same quantity of particles, the vision is continued, and only produces in us one single perception which preserves always the same relation to the object. Every conception, every sensible perception which bears upon the form or the other attributes of these images, is only the same form of the solid perceived directly, either in virtue of a sort of actual and continued condensation of the image, or in consequence of the traces which it has left in us.

Error and false judgments always depend upon the supposition that a preconceived idea will be confirmed, or at all events will not be overturned, by evidence. Then, when it is not confirmed, we form our judgment in virtue of a sort of initiation of the thoughts connected, it is true with the perception, and with a direct representation; but still connected also with a conception peculiar to ourselves, which is the parent of error. In fact the representations which intelligence reflects like a mirror, whether one perceives them in a dream, or by any other conceptions of the intellect, or of any other of the criteria, can never resemble the objects that one calls real and true, unless there were objects of this kind perceived directly. And, on the other side, error could not be possible if we did not receive some other motion also, a sort of initiative of intelligence connected; it is true with direct representation, but going beyond that representative. These conceptions being connected with the direct perception which produces the representation, but going beyond it, in consequence of a motion peculiar to the individual thought, produces error when it is not confirmed by evidence, or when it is contradicted by evidence; but when it is confirmed, or when it is not contradicted by evidence, then it produces truth.

We must carefully preserve these principles in order not to reject the authority of the faculties which perceive truth directly; and not, on the other hand, to allow what is false to be established with equal firmness, so as to throw everything into confusion.

Moreover, hearing is produced by some sort of current proceeding from something that speaks, or sounds, or roars, or in any manner causes any sort of audible circumstance. And this current is diffused into small bodies resembling one another in their parts; which, preserving not only some kind of relation between one another, but even a sort of particular identity with the object from which they emanate, puts us, very frequently, into a communication of sentiments with this object, or at least causes us to become aware of the existence of some external circumstance. If these currents did not carry with them some sort of sympathy, then there would be no such perception. We must not therefore think that it is the air which receives a certain form, under the action of the voice or of some other sound. For it is utterly impossible that the voice should act in this manner on the air. But the percussion produced in us when we, by the utterance of a voice, cause a disengagement of certain particles, constitutes a current resembling a light whisper, and prepares an acoustic feeling for us.

We must admit that the case of smelling is the same as that of hearing. There would be no sense of smell if there did not emanate from most objects certain particles capable of producing an impression on the smell. One class being ill-suited to the organ, and consequently producing a disordered state of it, the other being suited to it, and causing it no distress.

One must also allow that the atoms possess no one of the qualities of sensible objects, except form, weight, magnitude and anything else is unavoidably inherent in form; in fact, every quality is changeable, but the atoms are necessarily unchangeable; for it is impossible but that in the