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The Opinions of Philosophers about Perception. As soon as we attempt to penetrate into the opinions of the ancient philosophers in matters of science, as I think must have been experienced by every one who has undertaken the task, we find ourselves involved, like Eneas when he descended into the shades below, in darkness and obscurity; where every object is dimly seen through the mist; where we can with great difficulty grope our way; and where every shadowy form that floats before our eyes eludes grasp,
and when we essay to seize it, vanishes into air. This difficulty in ascertaining the sentiments of the ancients in matters of philosophy was, perhaps, from the nature of the case, to have been anticipated. Mankind in the constituent principles of their nature, and those moral and political relations in which they stand towards each other, are, for the most part, in all
ages of the world nearly the same. Hence those lessons of practical wisdom, and those combinations of ideas, which arise out of their moral and political condition, and are circulated among any people in their intercourse with one another, are easily conveyed from age to age, and
intelligible to the most remote posterity, as to those among whom they originated. But the case is quite different in matters of science and philosophy. The systems which are broached in these, seldom framed in the outset, out of the solid materials furnished by nature, but from the crude and perishing productions of human genius, having no archetype in nature, meet with the fate that attends all the monuments of human art and contrivance; have the period of their rise, prevalence and decay; until at length they perish, like the baseless fabricks of a vision, and
scarcely leave a wreck behind. When a system of philosophy unfounded in truth, and unsustained upon the firm basis of experience and observation, has thus passed away, the meaning of its terms of art is lost; and all those combinations of ideas, which were perfectly familiar to its votaries, during the period of its prevalence, are buried in oblivion.
To no part of science, perhaps, are these observations more applicable, than to that of the human mind, from the natural thinness and subtilty of the subject, and from the extreme difficulty which men always find in turning their attention inward, and reflecting upon the operations of the rational principle within them. For, as Mr. Locke finely remarks, the understanding, like the eye, whilst it makes us see all other things, takes no notice of itself; and it requires art and pains, to set it at a distance, and make it its own object, Notwithstanding, however, the darkness and obscurity which hang over the subject, we shall endeavour, as far as the labours of the learned enable us to proceed with tolerable certainty, to state the opinions of the ancients in reference to perception. Epicurus, who derived his doc. trines from Democritus, although as Cicero remarks he always injured them by mixtures of his own, appears to have been of opinion, that we become sensible of the qualities of outward objects by means of certain species or images, which are perpetually passing, like thin films from bodies, in form similar to the surfaces of the bodies themselves, and striking upon our organs. Thus the species or images of visible bodies consist in certain small particles of a peculiar magnitude, figure, and motion, which having passed in a certain situation from a body, penetrate the organ of sight, and effect it in a peculiar manner. Thus also, hearing is the effect of an efflux of certain particles from the body, which is the cause of the sound, so formed and arranged as when they strike upon the ear to become audible. The sensations
produced by means of the other senses admit of a similar explanation. These images passing from the object to the organ give us perceptions, and from thence proceeding to the place where the mind is, so act upon it, by means of the body, or occasion such motions or impressions upon that part of the corporeal system in which the soul is seated, as to occasion thought.* This is probably the original of the sensible species of the schoolmen, about which so much has been said; but it will be carefully remarked, that although we find here an hypothesis unsubstantiated by facts, yet even in this origin of the system, it is not maintained, as asserted by Dr. Reid, that these sensible species or images are the immediate objects of perception to the mind, but that they only occasion such motions or impressions in the bodily organs connected with the mind, as to cause perceptions or thoughts in it. The hypothesis, it is not to be denied, is untenable and fraught with absurdity, but nevertheless, let it be rightly understood; it supposed an image or species, like thin films, to pass from the object to the organ, and from thence to the sensorium or seat of the intellect; but it did not suppose that this image was the immediate object perceived by the mind, but only that by the action which it occasioned in the system of the nerves and brain, it produced both perception and thought; the first in the sertient, and the second, in the intellectual principle, into which they divided the soul.
From the doctrine thus expounded by Democritus, and his followers, let us proceed to that of Plato. A writer upon whom so many excellent judges bestowed such high encomiums, and whom Cicero does not hesitate to denominate, the Deus philosophorum, must, for the times in which he lived, have had extraordinary claims to merit. But this merit, resplendent as it must have been, is greatly obscured to our sight. Nothing can be more certain, than that his writings, ever since the period of their publication, have been more admired than understood. This writer's meaning, says the very learned Brucker, who has a right to pronounce an opinion, as with the aid of an excellent judgment and quick apprehension, he spent the greater portion of a long life, in searching out the theories of the ancient philosophers.—This writer's meaning, says he, is frequently lost in the obscurity of subtil distinctions; and sometimes after the Egyptian manner, concealed under the cloak of fables. The implicit followers of this philosopher, have been willing to exculpate their master from the charge of obscurity, by accusing his readers of dullness in their conceptions. But those who have attended to the origin of the Platonick philosophy will acknowledge, that it partakes largely of the character of subtilty and enthusiasm, which distinguished the Pythagorean system. In such a wondrous maze of words, does Plato involve his notions, that none of his disciples, not even the sagacious Stagyrite, could unfold them; and yet we receive them as sacred mysteries, and if we do not perfectly comprehend them, imagine that our intellects are too feeble to penetrate the conceptions of this divine philosopher; and that our eyes are blinded by that resplendent blaze of truth, upon which his eagle sight could gaze with: out injury. This will be acknowledged by every one, who, in perusing the philosophical writings of Plato, is capable of devesting himself of that blind respect for antiquity, by which the learned so frequently suffer themselves to be misled. In confirmation of the propriety of this judgment, we need only refer to the dialogue entitled Timæus, a chaotick mass of opinions, which no commentators have yet been able to reconcile or explain.” Such are the sentiments of Brucker, in regard to the writings of Plato. Of his philosophy, however, as far as it can be ascertained, amidst this ambiguity of expressions, the following account may be given, He
* See Brucker's History of Philosophy.
maintains that there were originally three principles, from which all things proceeded, God, matter, and ideas. God was the principle of intelligence, matter was eternal and infinite, and ideas were the eternal patterns or archetypes, according to which things were formed. Concerning these patterns or archetypes, he writes so obscurely, that his followers and interpreters, have been led to adopt very different opinions. Some, as those of the Alexandrian school, called the latter Platonists, affirm that the whole of Plato's doctrine, on the formation of the world, amounts to nothing more, than that the deity employed his understanding or reason in planning and executing the system of the universe; and consequently by ideas, eicones or paradeigmata, existing in the reason of God, are only meant conceptions in the divine mind. This view of the subject entertained by the latter Platonists, is certainly the only one which renders his doctrine rational or intelligible; since the Deity must have had his plans, before he proceeded to the formation of the universe. In favour of this opinion too, we find no less an author than the learned Dr. Cudworth, who, in his intellectual system, speaks in the following style. After quoting the opinion of Tertullian in his book, de anima, which is in these words; vult Plato esse quasdam substantias invisibiles, incorporeales, supermundiales, divinas et eternas, quas appellat ideas, id est formas et exempla, et causas naturalium istorum manifestorum et subjacentium corporalibus; et illas quidem esse veritates, hæc autem imagines earum-thus translated by him; Plato conceiveth that there are certain substances, invisible, incorporeal, supermundial, divine and eternal, which he calls ideas, that is, forms, exemplars, and causes of all these natural and sensible things, they being the truths, but the other the images; he proceeds—“ Neither can it be denied, that there are some odd expressions in Plato, sounding this way; who, therefore, may not be justified in this, nor I think in some other conceits of his, concerning