little can we know whether this power must be limited to things present and in contact with us. Neither can any man pretend to prove that the Being who gave us the power to perceive things present, may not give us the power to perceive things distant, to remember things past, and to conceive things that never existed.”1

In another part of his work, Dr. Reid has occasion to trace the origin of the prejudice which has led philosophers to suppose, that in all the operations of the understanding there must be an object of thought, which really exists while we think of it. His remarks on this subject, which are highly ingenious and satisfactory, are contained in his account of the different theories concerning conception.2

As in all the ancient metaphysical systems it was taken for granted, (probably from the analogy of our external perceptions,) that every exertion of thought implies the existence of an object distinct from the thinking being; it naturally occurred, as a very curious question, What is the immediate object of our attention when we are engaged in any general speculation? or, in other words, what is the nature of the idea corresponding to a general term? When I think of any particular object which I have formerly perceived, such as a particular friend, a particular tree, or a particular mountain, I can comprehend what is meant by a picture or representation of such objects; and therefore the explanation given by the ideal theory of that act of the mind which we formerly called Conception, if not perfectly satisfactory, is at least not wholly unintelligible. But what account shall we give, upon the principles of this theory, of the objects of my thoughts, when I employ the words, friend, tree, mountain, as generic terms? For that all the things I have ever perceived are individuals; and, consequently, that the ideas denoted by general words, (if such ideas exist,) are not copied from any originals that have fallen under my observation, is not only self-evident, but almost an identical proposition.

In answer to this question, the Platonists, and at a still 1 Essays on the Intellectual Powers, p. 214. Ibid. p. 378.

earlier period, the Pythagoreans taught, that although these universal ideas are not copied from any objects perceivable by sense, yet that they have an existence independent of the human mind, and are no more to be confounded with the understanding, of which they are the proper objects, than material things are to be confounded with our powers of external perception; that as all the individuals which compose a genus must possess something in common, and as it is in consequence of this that they belong to that genus, and are distinguishable by the same name, this common thing forms the essence of each, and is the object of the understanding, when we reason concerning the genus. They maintained also, that this common essence,1 notwithstanding its inseparable union with a multitude of different individuals, is in itself one, and indivisible.

On most of these points the philosophy of Aristotle seems to have coincided very nearly with that of Plato. The language, however, which these philosophers employed on this subject was different, and gave to their doctrines the appearance of a wider diversity than probably existed between their opinions. While Plato was led, by his passion for the marvellous and the mysterious, to insist on the incomprehensible union of the same idea or essence, with a number of individuals without multiplication or division,2 Aristotle, more cautious, and aiming at greater perspicuity, contented himself with saying, that all individuals are composed of matter and form; and that it is in consequence of possessing a common form, that different

"is that which makes one of the many; which, preserving the unity and integrity of its own nature, runs through and mixes with things infinite in number; and yet, however multiform it may appear, is always the same; so that by it we find out and discriminate the thing, whatever shapes it may assume, and under whatever disguise it may conceal itself."-- Plato in Philebo; (quoted by the author of The Origin and Progress of Language, vol. i. p. 100, 2d edit.)

individuals belong to the same genus. But they both agreed, that as the matter, or the individual natures of objects were perceived by sense, so the general idea, or essence, or form, was perceived by the intellect; and that as the attention of the vulgar was chiefly engrossed with the former, so the latter furnished to the philosopher the materials of his speculations.

ence.

The chief difference between the opinions of Plato and Aristotle on the subject of ideas, related to the mode of their existThat the matter of which all things are made existed from eternity, was a principle which both admitted; but Plato farther taught, that of every species of things there is an idea. of form which also existed from eternity; and that this idea is the exemplar or model according to which the individuals of the species were made; whereas Aristotle held, that although matter may exist without form, yet that forms could not exist without matter.1

The doctrine of the Stoics concerning universals, differed widely from those both of Plato and Aristotle, and seems to have approached to a speculation which is commonly supposed

1 In this account of the difference between Plato and Aristotle on the subject of ideas, I have chiefly followed Brucker, whose very laborious researches with respect to this article of the history of philosophy are well known. In stating the distinction, however, I have confined myself to as general terms as possible; as the subject is involved in much obscurity, and has divided the opinions of very eminent writers. The reader will find the result of Brucker's inquiries, in his own words, in Note F. The authority of Brucker, in this instance, has the more weight with me, as it coincides in the most material respects with that of Dr. Reid. See his Essays on the Intellectual Powers of Man, and the conclusion of his Inquiry into the Human Mind.

A very different account of Aristotle's doctrine, in those particulars in which it is commonly supposed to differ from

that of Plato, is given by two modern writers of great learning, whose opinions are justly entitled to much respect, from their familiar acquaintance with Aristotle's latter Commentators of the Alexandrian School.-See [Monboddo's] Origin and Progress of Language, vol. i., and Harris's Hermes.

It is of no consequence for any of the purposes which I have at present in view, what opinion we form on this much controverted point of philosophical history. In so far as the ideal theory was an attempt to explain the manner in which our general speculations are carried on, it is agreed on all hands, that the doctrines of Plato and Aristotle were essentially the same; and accordingly, what I have said on that subject, coincides entirely with a passage which the reader will find in Origin and Progress of Language, vol. i. p. 38, 2d edit.

to be of a more recent origin, and which an eminent philosopher of the present age has ranked among the discoveries which do the greatest honour to modern genius.1

Whether this doctrine of the Stoics coincided entirely with that of the Nominalists, (whose opinions I shall afterwards endeavour to explain,) or whether it did not resemble more a doctrine maintained by another sect of schoolmen called Conceptualists, I shall not inquire. The determination of this question is interesting only to men of erudition; for the knowledge we possess of this part of the Stoical philosophy is too imperfect to assist us in the farther prosecution of the argument, or even to diminish the merit of those philosophers who have in modern times been led to similar conclusions.2

As it is not my object in this work to enter into historical details, any farther than is necessary for illustrating the subjects of which I treat, I shall pass over the various attempts which were made by the Eclectic philosophers, (a sect which arose at Alexandria about the beginning of the third century,) to reconcile the doctrines of Plato and Aristotle concerning ideas. The endless difficulties, it would appear, to which their speculations led, induced at last the more cautious and modest inquirers to banish them entirely from Dialectics, and to content themselves with studying the arrangements or classifications of universals which the ancient philosophers had made, without engaging in any metaphysical disquisitions concerning their nature. Porphyry, in particular, although he tells us that he has speculated much on this subject, yet in his Introduction to Aristotle's Categories, waves the consideration of it as obscure and intricate. On such questions as these: "Whether genera and species exist in Nature, or are only conceptions of the Human Mind; and, (on the supposition that they exist in nature,) whether they are inherent in the objects of sense, or disjoined from them ?" he declines giving any determination.

This passage in Porphyry's Introduction is an object of curiosity; as by a singular concurrence of circumstances, it served to perpetuate the memory of a controversy from which it was 1 Treatise of Human Nature, book i. part i. sect. 7. 2 See Note G.

the author's intention to divert the inquiries of his readers. Amidst the disorders produced by the irruptions of the Barbarians, the knowledge of the Greek tongue was almost entirely lost, and the studies of philosophers were confined to Latin versions of Aristotle's Dialectics, and of Porphyry's Introduction concerning the Categories. With men who had a relish for such disquisitions, it is probable that the passage already quoted from Porphyry would have a tendency rather to excite than to damp curiosity; and accordingly, we have reason to believe, that the controversy to which it relates continued during the dark ages to form a favourite subject of discussion. The opinion which was prevalent was, (to use the scholastic language of the times,) that universals do not exist before things, nor after things, but in things; that is, (if I may be allowed to attempt a commentary upon expressions to which I do not pretend to be able to annex very precise notions,) universal ideas have not (as Plato thought) an existence separable from individual objects; and therefore they could not have existed prior to them in the order of time; nor yet (according to the doctrine of the Stoics) are they mere conceptions of the mind, formed in consequence of an examination and comparison of particulars; but these ideas or forms are from eternity united inseparably with that matter of which things consist; or, as the Aristotelians sometimes express themselves, the forms of things are from eternity immersed in matter. The reader will, I hope, forgive me for entering into these details, not only on account of their connexion with the observations which are to follow, but as they relate to a controversy which, for many ages, employed all the ingenuity and learning in Europe, and which, therefore, however frivolous in itself, deserves the attention of philosophers, as one of the most curious events which occurs in the history of the Human Mind.

Such appears to have been the prevailing opinion concerning the nature of universals till the eleventh century, when a new doctrine, or (as some authors think) a doctrine. borrowed from the school of Zeno, was proposed by Roscelinus,1

1 See Note H.