IV. quifite in every cafe in which abftraction is fubfervient to the CHA P. power of reafoning; for it frequently happens, that we can reafon concerning one quality or property of an object abftracted from the reft, while, at the fame time, we find it impoffible to conceive it separately. Thus, I can reafon concerning extenfion and figure, without any reference to colour; although it may be doubted, if a person poffeffed of fight can make extenfion and figure fteady objects of conception, with-out connecting with them one colour or another. Nor is this: always owing (as it is in the instance now mentioned) merely to the affociation of ideas; for there are cafes, in which we can. reafon concerning things feparately, which it is impoffible for us to fuppofe any being fo conftituted as to conceive apart. Thus, we can reafon concerning length, abftracted from any other dimension; although, furely, no understanding can make length, without breadth, an object of conception. And, by the way, this leads me to take notice of an error, which mathematical teachers are apt to commit, in explaining the first principles of geometry. By dwelling By dwelling long on Euclid's firft definitions, they lead the ftudent to fuppofe that they relate to notions which are extremely myfterious; and to ftrain his powers in fruitless attempts to conceive, what cannot poffibly be made an object of conception. If thefe definitions were omitted, or very flightly touched upon, and the attention at once directed to geometrical reafonings, the ftudent would immediately perceive, that although the lines in the diagrams are really extended in two dimenfions, yet that the demonstrations relate only to one of them; and that the human understanding has the faculty of reafoning concerning things feparately, which are always IV. CHAP, always presented to us, both by our powers of perception and conception, in a state of union. Such abstractions, in truth, are familiar to the most illiterate of mankind; and it is in this very way that they are infenfibly formed. When a tradesman fpeaks of the length of a room, in contradiftinction to its breadth; or when he speaks of the distance between any two objects; he forms exactly the fame abftraction, which is referred to by Euclid in his fecond definition; and which most of his commentators have thought it neceffary to illuftrate by prolix metaphyfical difquifitions. I SHALL only obferve farther, with respect to the nature and province of this faculty of the mind, that notwithstanding its effential fubferviency to every act of claffification, yet it might have been exercised, although we had only been acquainted with one individual object. Although, for example, we had never feen but one rofe, we might still have been able to attend to its colour, without thinking of its other properties. This has led fome philofophers to suppose, that another faculty besides abstraction, to which they have given the name of generalisation, is neceffary to account for the formation of genera and fpecies; and they have endeavoured to fhew, that although generalisation without abftraction is impoffible; yet that we might have been fo formed, as to be able to abstract, without being capable of generalifing. The grounds of this opinion, it is not necessary for me to examine, for any of the purposes which I have at present in view. SECTION II. Of the Objects of our Thoughts, when we employ general FROM ROM the account which was given in a former chapter, of the common theories of perception, it appears to have been a prevailing opinion among philofophers, that the qualities of external objects are perceived, by means of images or fpecies tranfmitted to the mind by the organs of fense: an opinion of which I already endeavoured to trace the origin, from certain natural prejudices fuggefted by the phenomena of the material world. The fame train of thinking has Ied them to fuppofe that, in the cafe of all our other intellectual operations, there exift in the mind certain ideas diftinct from the mind itself; and that these ideas are the objects about which our thoughts are employed. When I recollect, for example, the appearance of an absent friend, it is supposed that the immediate object of my thought is an idea of my friend; which I at first received by my fenfes, and which I have been enabled to retain in the mind by the faculty of memory. When I form to myself any imaginary combination by an effort of poetical invention, it is fuppofed, in like manner, that the parts which I combine, existed previously in the mind; and furnish the С НАР: IV. IV. CHAP. the materials on which it is the province of imagination to operate. It is to Dr. Reid we owe the important remark, that all thefe notions are wholly hypothetical; that it is impoffible to produce a fhadow of evidence in fupport of them; and that, even although we were to admit their truth, they would not render the phenomena in queftion more intelligible. According to his principles, therefore, we have no ground for fupposing, that, in any one operation of the mind, there exifts in it an object diftinct from the mind itfelf; and all the common expreffions which involve fuch a fuppofition, are to be confidered as unmeaning circumlocutions, which ferve only to disguise from us the real history of the intellectual phenomena *. WE * In order to prevent misapprehenfions of Dr. Reid's meaning, in his reasonings against the ideal theory, it may be neceffary to explain, a little more fully than I have done in the text, in what fenfe he calls in queftion the existence of ideas for the meaning which this word is employed to convey in popular difcourse, differs widely from that which is annexed to it by the philofophers whofe opinion he controverts. This explanation I shall give in his own words : "In popular language, idea fignifies the fame thing as conception, apprehen"fion, notion. To have an idea of any thing, is to conceive it. To have a "diftinct idea, is to conceive it diftinctly. To have no idea of it, is not to "conceive it at all.-When the word idea is taken in this popular fenfe, no man can poffibly doubt whether he has ideas." "According to the philofophical meaning of the word idea, it does not fig"nify that act of the mind which we call thought, or conception, but fome "object of thought. Of thefe objects of thought called ideas, different sects of philofophers have given very different accounts." "Some have held them to be self-exiftent; others to be in the divine mind; "others in our own minds; and others in the brain, or fenforium." p. 213. "The Peripatetick fyftem of fpecies and phantafms, as well as the Platonick "fyftem of ideas, is grounded upon this principle, that in every kind of thought, "there 4 IV. "We are at a loss to know," (fays this excellent philofopher,) CHA P. "how we perceive distant objects; how we remember things paft; how we imagine things that have no existence. Ideas "in the mind feem to account for all thefe operations: they are all by the means of ideas reduced to one operation; to a "kind of feeling, or immediate perception of things prefent, ❝and in contact with the percipient; and feeling is an opera"tion fo familiar, that we think it needs no explanation, but may serve to explain other operations." "BUT this feeling, or immediate perception, is as difficult "to be comprehended, as the things which we pretend to ex "there must be some object that really exifts; in every operation of the mind, "fomething to work upon. Whether this immediate object be called an idea "with Plato, or a phantafm or species with Ariftotle; whether it be eternal and "uncreated, or produced by the impreffions of external objects, is of no confequence in the present argument." Ibid. p. 388. "So much is this opinion fixed in the minds of philofophers, that, I doubt "not but it will appear to moft, a very strange paradox, or rather a contra"diction, that men should think without ideas. But this appearance of con"tradiction arises from the ambiguity of the word idea. If the idea of a thing "means only the thought of it, which is the most common meaning of the "word, to think without ideas, is to think without thought; which is un"doubtedly a contradiction. But an idea, according to the definition given of "it by philofophers, is not thought, but an object of thought, which really "exifts, and is perceived, &c." Ibid. p. 390. I have only to add, that when, in this work, I make use of the word idea in ftating my own opinions, I employ it uniformly in the popular sense, and not in the philofophical fenfe, as now explained: it would be better, perhaps, to avoid it altogether; but I have found it difficult to do fo, without adopting unusual modes of expreffion. I flatter myself that I have used it with due caution. |