10 The parallel motion of the eyes, as necessary to distinct vision. 11 The sense of veracity, or a disposition to speak truth.

12 A sense of credulity, or a disposition to believe others. 13 The inductive faculty, by which we infer similar effects from similar causes.

To this table Priestley has subjoined (under the title of Autho rities) a series of quotations from Reid's Inquiry, which he seems to have considered as justifying the statement which the table exhibits of the leading opinions contained in that work. How far the statement is correct, those who have at all entered into the spirit of Reid's reasonings, will be able to judge completely from the 4th and 5th articles ;-according to which, Reid is represented as having maintained, that a hard substance suggests the sensation of hardness, and the belief of something hard ;—an extended substance, the idea of extension and space;—and the primary qualities of bodies in general, their peculiar sensations.The authority produced for the first of these charges is the following sentence:

"By an original principle of our constitution, a certain sen"sation of touch both suggests to the mind the conception of "hardness, and creates the belief of it; or, in other words, this "sensation is a natural sign of hardness."

It is perfectly evident that the authority here is not only at variance with the charge, but is in direct opposition to it. Ac cording to Reid, the sensation suggests the conception of hardness; according to Priestley's comment, he maintains the absurd and nonsensical proposition, that "a hard substance suggests the "sensation of hardness."-The other two misrepresentations are equally gross; and, indeed, precisely of the same description.

Note (B.) p. 72.

That there are many words used in philosophical discourse, which do not admit of logical definition, is abundantly manifest. This is the case with all those words that signify things uncom pounded, and consequently unsusceptible of analysis ;-a proposition, one should think, almost self-evident; and yet it is surprising how very generally it has been overlooked by philosophers.

That Aristotle himself, with all his acuteness, was not aware of it, appears sufficiently from the attempts he has made to define various words denoting some of the simplest and most elementary objects of human thought. Of this, remarkable instances occur in his definitions of ́time and of motion; definitions which were long

the wonder and admiration of the learned; but which are now remembered only from their singular obscurity and absurdity. It is owing to a want of attention to this circumstance, that metaphysicians have so often puzzled themselves about the import of terms, employed familiarly, without the slightest danger of mistake, by the most illiterate ;-imagining, that what they could not define must involve some peculiar mystery; when, in fact, the difficulty of the definition arose entirely from the perfect simplicity of the thing to be defined. "Quid sit Tempus," said St Augustine, "si nemo quærat a me, scio; si quis interroget, nescio."

According to Dr Reid, Descartes and Locke are the earliest writers in whom this fundamental principle of logic is to be found. Locke seems to have considered the merit of introducing it as exclusively his own. (Essay, Book III. chap. iv. § iv.) Neither of these statements is quite correct. I do not know if Locke himself has expressed the doctrine in question more clearly than our celebrated Scottish lawyer Lord Stair, in a work published several years before the Essay on Human Understanding; and it is worthy of observation, that if the French Philosopher had the start of our countryman in perceiving its truth and importance, when applied to the Philosophy of the Mind, he was by no means so fully aware of the attention due to it, in explaining the first principles of Physical Science.

"Necesse est quosdam terminos esse adeo claros, ut clarioribus "elucidari nequeant, alioquin infinitus esset progressus in ter"minorum explicatione, adeo ut nulla possit esse clara cognitio, nec ullus certo scire possit alterius conceptus."

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"Tales termini sunt Cogitatio, Motus, quibus non dantur cla"riores conceptus aut termini, et brevi apparebit, quam inutiliter "Aristoteles et Cartesius conati sunt definire Motum.”

Physiologia Nova Experimentalis, &c. (p. 9.) Authore D. de Stair, Carolo II. Britanniarum Regi a Consiliis Juris et Status. Ludg. Batav. 1686.-See also p. 79 of the same book.

Locke's Essay (as appears from the dedication) was first printed in 1689. Lord Stair's work must have been published a considerable time before. The Latin translation of it (which is the only edition I have seen) is dated 1686; and bears, on the titlepage, that the original had appeared before. Nuper Latinitate

donata.

According to a learned and ingenious writer, Aristotle himself "had taught, before Mr Locke, that what the latter calls simple " ideas could not be defined."—(Translation of Aristotle's Ethics and Politics, by Dr Gillies, Vol. I. p. 138, 2d edit.) The passages, however, to which he has referred, seem to me much less decisive evidence in support of this assertion, than Aristotle's own definitions are against it. Nor can I bring myself to alter this opinion, even by Dr Gillies's attempt to elucidate the celebrated definition of Motion.

Note (C.) p. 91.

It may be of use to some of my readers, before proceeding to the third chapter, to read with attention the following extracts from Dr Reid:

"The word idea occurs so frequently in modern philosophical writings upon the mind, and is so ambiguous in its meaning, "that it is necessary to make some observations upon it. There 66 are chiefly two meanings of this word in modern authors, a po. "pular and a philosophical.

First, in popular language, idea signifies the same thing as conception, apprehension, notion. To have an idea of any thing, "is to conceive it. To have a distinct idea, is to conceive it dis. "tinctly. To have no idea of it, is not to conceive it at all.

"When the word is taken in this popular sense, no man can For he that doubts must "possibly doubt whether he has ideas. "think, and to think is to have ideas.

"Secondly, According to the philosophical meaning of the "word idea, it does not signify that act of the mind which we cali "thought or conception, but some object of thought. Ideas, "according to Mr Locke (whose frequent use of this word has

probably been the occasion of its being adopted into common "language), are nothing but the immediate objects of the mind "in thinking.' But of those objects of thought called ideas, dif❝ferent sects of philosophers have given a very different ac4 count.

"Mr Locke, who uses the word idea so very frequently, tells us, that he means the same thing by it as is commonly meant "by species or phantasm. Gassendi, from whom Locke bor"rowed more than from any other author, says the same. "words species and phantasm are terms of art in the Peripatetic system, and the meaning of them is to be learned from it.

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Modern philosophers, as well as the Peripatetics of old, have "conceived, that external objects cannot be the immediate ob. "jects of our thought; that there must be some image of them in "the mind itself, in which, as in a mirror, they are seen. And the

name idea, in the philosophical sense of it, is given to those "internal and immediate objects of our thoughts. The external "thing is the remote or mediate object; but the idea or image of "that object in the mind is the immediate object, without which "we could have no perception, no remembrance, no conception of the mediate object.

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"When, therefore, in common language, we speak of having an idea of any thing, we mean no more by that expression but "thinking of it. The vulgar allow, that this expression implies

a mind that thinks; and an act of that mind which we call "thinking. But besides these, the philosopher conceives the existence of an idea which is the immediate object of thought. The idea is in the mind itself, and can have no existence but in

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a mind that thinks; but the remote or mediate object may be ચંદ something external, as the sun or moon; it may be something past or future; it may be something which never existed. This "is the philosophical meaning of the word idea; and we may ob. 66 serve, that this meaning of that word is built upon a philosoઠંડ phical opinion: For, if philosophers had not believed that there 66 are such immediate objects of all our thoughts in the mind, "they would never have used the word idea to express them.

"I shall only add on this article, that, although I may have "occasion to use the word idea in this philosophical sense, in explaining the opinions of others, I shall have no occasion to 66 use it in expressing my own, because I believe ideas, taken in "this sense, to be a mere fiction of philosophers. And, in the "popular meaning of the word, there is the less occasion to use "it, because the English words thought, notion, apprehension, (6 answer the purpose as well as the Greek word idea; with this "advantage, that they are less ambiguous."-Essays on the Intellectual Powers, p. 22, et seq.

After this long quotation from Dr Reid, it is proper to mention what has induced me to make an occasional use, in these Essays, of a word which he has taken so much pains to discard from the language of philosophy.

My reason is shortly this, that finding, after all he has written on the subject, the word idea still maintains, and is likely long to maintain its ground, it seemed to me a more practicable attempt to limit and define its meaning, than to banish it altogether. For this purpose, I generally couple it with some synonymous word, such as thought or notion, so as to exclude completely all the theoretical doctrines usually implied in it; and I cannot help flattering myself with the hope, that, in this way, I may be able to contribute something towards the gradual extirpation of the prejudices, to which, in its philosophical acceptation, it has hitherto given so powerful a support.

It may gratify the curiosity of some of my readers, to be able to compare the language of Descartes concerning ideas, with that of Mr Locke. According to the first of these writers, 66 an idea "is the thing thought upon, as far as it is objectively in the un"derstanding." Idea est ipsa res cogitata, quatenus est objective in intellectu. By way of comment upon this, he tells us afterwards, in reply to a difficulty started by one of his correspondents ; ubi advertendum, me loqui de idea quæ nunquam est ex"tra intellectum, et ratione cujus esse objective non aliud significat,, "quàm esse in intellectu eo modo quo objecta in illo esse solent." -Responsio ad Primas Objectiones in Meditationes Cartesii.

I may not have a better opportunity of observing afterwards, that Descartes rejected entirely that part of the Peripatetic system which accounts for perception by species or ideas proceeding from external things, and transmitted to the mind through the

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channel of the senses. His arguments against that hypothesis were so clear and conclusive, that Gravesande, in a small treatise pub. lished in 1737, speaks of it as unworthy of refutation: Explo sam dudum, de speciebus à rebus procedentibus, et menti impres "sis, sententiam explicare et refellere, inutile credimus." -Introductio ad Philosophiam, p. 98.

While Descartes, however, dissented on this point from the schoolmen, he maintained, in common with them, that what we immediately perceive is not the external object, but an idea or image of it in our mind.

Among our later writers, I do not recollect any who have entered into so elaborate an explanation of the nature of ideas, considered as the objects of thought, as the ingenious author of a work entitled, The Light of Nature Pursued. The following passage, which he gives as the substance of his own creed on this point, is, I suspect, a tolerably faithful exposition of prejudices which still remain in most minds; and which are insensibly imbibed in early life, from the hypothetical phraseology bequeathed to us by the schoolmen.

"Idea is the same as image, and the term imagination implies a "receptacle of images: but image being appropriated, by com"mon use, to visible objects, could not well be extended to other "things without confusion; wherefore learned men have import. "ed the Greek word idea, signifying image or appearance, to "which, being their own peculiar property, they might affix as "large a signification as they pleased. For the image of a sound, "or of goodness, would have offended our delicacy, but the idea "of either goes down glibly: therefore, idea is the same with re"spect to things in general, as image with respect to objects of ❝ vision.

"In order to render the notion of ideas clearer, let us begin "with images. When a peacock spreads his tail in our sight, 66 we have a full view of the creature with all his gaudy plumage "before us; the bird remains at some distance, but the light re "flected from him paints an image upon our eyes, and the optic ❝ nerves transmit it to the sensory. This image, when arrived at "the ends of the nerves, becomes an idea, and gives us our dis"cernment of the animal; and after the bird is gone out of view, 66 we can recal the idea of him to perform the same office as bo

Mr Hume afterwards relapsed into the old scholastic language on this subject: "The slightest philosophy teaches us, that nothing can ever be pre"sent to the mind but an image or perception; and that the senses are only "the inlets through which these are received, without being ever able to "produce any immediate intercourse between the mind and the object." -Essays.

How this language is to be reconciled with the philosophy which teaches, that ideas or images can have no existence but in a mind, Mr Hume has not attempted to explain.