344 ON HUMAN UNDERSTANDING. 



pose of trying their comparative pretensions, and of submitting them to your 

 impartial award. 



The principal systems that were started among the philosophers of Greece 

 to explain the origin and value of human knowledge were those of Plato, of 

 Aristotle, of Epicurus, and of the skeptics, especially Pyrrho and Arcesilas ; 

 and the principal systems to which they have given birth in later or modern 

 times, are those of Des Cartes, Locke, Berkeley, Hume, Hartley, Kant, and 

 the Scottish School of Common Sense, at the head of which we are to place 

 Dr. Reid. 



I had occasion to observe, in our first series of lectures,* that it was a dogma 

 common to many of the Greek schools, that matter, though essentially eter 

 nal, is also, in its primal and simple state, essentially amorphous, or desti 

 lute of all form and quality whatever ; and I farther remarked, that the ground- 

 work of this dogma consisted in a belief that form and quality are the con 

 trivance of an intelligent agent ; while matter, though essentially eternal, is 

 essentially unintelligent. Matter, therefore, it was contended, cannot possi- 

 bly assume one mode of form rather than another mode ; for if it were capa- 

 ble of assuming any kind, it must have been capable of assuming every kind 

 and of course of exhibiting intelligent effects without an intelligent cause. 



Form, then, according to the Platonic schools, in which this was princi- 

 pally taught, existing distinct from matter by the mere wi*ll of the Great First 

 Cause, presented itself, from all eternity, to his wisdom or logos, in every 

 possible variety ; or, in other words, under an infinite multiplicity of incor- 

 poreal or intellectual patterns, exemplars, or archetypes, to which the founder 

 of this school gave the name of ideas ; a term that has descended without any 

 mischief into the popular language of our own day ; but which, in the hands 

 of the schoolmen, and various other theorists, has not unfrequently been pro- 

 ductive of egregious errors and abuses. By the union of these intellectual 

 archetypes with the whole or with any portion of primary or incorporeal mat- 

 ter, matter immediately becomes imbodied, assumes palpable forms, corres- 

 pondent with the archetypes united with it, and is rendered an object of per- 

 ception to the external senses ; the mind, or intelligent principle itself, how- 

 ever, which is an emanation from the Great Intelligent Cause, never perceiv- 

 ing any thing more than the intellectual or formative ideas of objects as they 

 are presented to the senses, and reasoning concerning them by those ideas 

 alone. 



It must be obvious, however, that the mind is possessed of many ideas 

 which it could not derive from a material source. Such are all those that re- 

 late to abstract moral truths and pure mathematics. And to account for 

 these, it was a doctrine of the Platonic philosophy, that, besides the sensible 

 world, there is also an intelligible world ; that the mind of man is equally 

 connected with both, though the latter cannot possibly be discerned by cor- 

 poreal organs ; and that, as the mind perceives and reasons upon sensible ob- 

 jects by means of sensible archetypes or ideas, so it perceives and reasons 

 upon intelligible objects by means of intelligible ideas. 



The only essential variation from this hypothesis which Aristotle appears 

 to have introduced into his own, consists in his having clothed, 'if I may be 

 allowed the expression, the naked ideas of Plato, with the actual qualities of 

 the objects perceived ; his doctrine being, that the sense, on perceiving or 

 being excited by an external object, conveys to the mind a real resemblance 

 of it ; which, however, though possessing form, colour, and other qualities of 

 matter, is not matter itself, but an unsubstantial image, like the picture in a 

 mirror; as though the mind itself were a kind of mirror, and had a power of 

 reflecting the image of whatever object is presented to the external senses. 

 This unsubstantial image or picture, in order to distinguish it from the intel- 

 lectual pattern or idea of Plato, he denominated a phantasm. And as he sup- 

 ported with Plato the existence of an intelligible as well as of a sensible 

 world, it was another part of his hypothesis that, while things sensible are 



* SortfS i Lecture U. 



