which he made to psychology, would declare the influence he has had on human opinion. From this immateriality, however, he did not derive the tenet of its immortality. He was justly contented to say, that from the intrinsic difference between mind and body, the dissolution of the one could not necessarily take away the existence of the other, but that it was for God to determine whether it should continue to exist; and this determination, as he thought, could only be learned from his revealed will. The more powerful arguments, according to general apprehension, which reason affords for the sentient being of the soul after death, did not belong to the metaphysical philosophy of Descartes, and would never have been very satisfactory to his mind. He says, in one of his letters, that 'laying aside what faith assures us of, he owns that it is more easy to make conjectures for our own advantage, and entertain promising hopes, than to feel any confidence in their accomplishment."

66

tion of de

finitions.

101. Descartes was perhaps the first who saw that deHis just no- finitions of words, already as clear as they can be made, are nugatory or impracticable. This alone would distinguish his philosophy from that of the Aristotelians, who had wearied and confused themselves for twenty centuries with unintelligible endeavours to grasp by definition what refuses to be defined. "Mr. Locke, says Stewart, "claims this improvement as entirely his own, but the merit of it unquestionably belongs to Descartes, although it must be owned that he has not always sufficiently attended to it in his researches." A still

Vol. ix. p. 369.

Dissertation, ubi suprà. Stewart, in his Philosophical Essays, note A, had censured Reid for assigning this remark to Descartes and Locke, but without giving any better reason than that it is found in a work written by Lord Stair; earlier, certainly, than Locke, but not before Descartes. It may be doubtful, as we shall see hereafter, whether Locke has not gone beyond Descartes, or at least distinguished undefinable words more strictly.

[Sir William Hamilton remarks on this passage, where Reid assigns the observation to Descartes and Locke: "This is incorrect. Descartes has little, and Locke no praise for this observation. It had been made by Aristotle, and after him by many others; while, subsequently

to Descartes, and previous to Locke, Pascal, and the Port-Royal logicians, to say nothing of a paper of Leibnitz in 1684, had reduced it to a matter of common-place. In this instance, Locke can indeed be proved a borrower." Hamilton's edition of Reid, p. 220. But this very learned writer quotes no passage from Aristotle to this effect, and certainly the practice of that philosopher and his followers was to attempt definitions of every thing. Nor could Aristotle, or even Descartes, have distinguished undefinable words by their expressing simple ideas of sense or reflection, as Locke has done, when they have not made that classification of ideas into simple and complex, which forms so remarkable a part of his philosophy.-1847.]

more decisive passage to this effect than that referred to by Stewart in the Principia will be found in the posthumous dialogue on the Search after Truth. It is objected by one of the interlocutors, as it had actually been by Gassendi, that, to prove his existence by the act of thinking, he should first know what existence and what thought is. "I agree with you," the representative of Descartes replies, "that it is necessary to know what doubt is, and what thought is, before we can be fully persuaded of this reasoning-I doubt, therefore I am or what is the same I think, therefore I am. But do not imagine that for this purpose you must torture your mind to find out the next genus, or the essential differences, as the logicians, talk and so compose a regular definition. Leave this to such as teach or dispute in the schools. But whoever will examine things by himself, and judge of them according to his understanding, cannot be so senseless as not to see clearly, when he pays attention, what doubting, thinking, being, are, or to have any need to learn their distinctions. Besides, there are things which we render more obscure in attempting to define them, because, as they are very simple and very clear, we cannot know and comprehend them better than by themselves. And it should be reckoned among the chief errors that can be committed in science for men to fancy that they can define that which they can only conceive, and distinguish what is clear in it from what is obscure, while they do not see the difference between that which must be defined before it is understood, and that which can be fully known by itself. Now, among things which can thus be clearly known by themselves, we must put doubting, thinking, being. For I do not believe any one ever existed so stupid as to need to know what being is before he could affirm that he is; and it is the same of thought and doubt. Nor can he learn these things except by himself, nor be convinced of them but by his own experience, and by that consciousness and inward witness which every man finds in himself when he examines the subject. And as we should define whiteness in vain to a man who can see nothing, while one who can open his eyes and see a white object requires no more, so to know what doubting is, and what thinking is, it is

a

only necessary to doubt and to think." Nothing could more tend to cut short the verbal cavils of the schoolmen, than this limitation of their favourite exercise, definition. It is due, therefore, to Descartes, so often accused of appropriating the discoveries of others, that we should establish his right to one of the most important that the new logic has to boast.

of sub

stances

102. He seems, at one moment, to have been on the His notion point of taking another step very far in advance of his age. "Let us take," he says, "a piece of wax from the honey-comb: it retains some taste and smell, it is hard, it is cold, it has a very marked colour, form, and size. Approach it to the fire; it becomes liquid, warm, inodorous, tasteless; its form and colour are changed, its size is increased. Does the same wax remain after these changes? It must be allowed that it does; no one doubts it, no one thinks otherwise. What was it then that we so distinctly knew to exist in this piece of wax? Nothing certainly that we observed by the senses, since all that the taste, the smell, the sight, the touch reported to us has disappeared, and still the same wax remains.' This something which endures under every change of sensible qualities cannot be imagined; for the imagination must represent some of these qualities, and none of them are essential to the thing; it can only be conceived by the understanding.b

not quite correct.

103. It may seem almost surprising to us, after the writings of Locke and his followers on the one hand, and the chemist with his crucible on the other, have chased these abstract substances of material objects from their sanctuaries, that a man of such prodigious acuteness and intense reflection as Descartes should not have remarked that the identity of wax after its liquefaction is merely nominal, and depending on arbitrary language, which in many cases gives new appellations to the same aggregation of particles after a change of their sensible qualities; and that all we call substances are but aggregates of resisting movable corpuscles, which by the laws of nature are capable of affecting our senses differently, according to the combinations they may enter into,

a Vol. xi. p. 369.

b Méditation Seconde, i. 256.

and the changes they may successively undergo. But if he had distinctly seen this, which I do not apprehend that he did, it is not likely that he would have divulged the discovery. He had already given alarm to the jealous spirit of orthodoxy by what now appears to many so selfevident, that they have treated the supposed paradox as a trifling with words, the doctrine that colour, heat, smell, and other secondary qualities, or accidents of bodies, do not exist in them, but in our own minds, and are the effects of their intrinsic or primary qualities. It was the tenet of the schools that these were sensible realities, inherent in bodies; and the church held as an article of faith that the substance of bread being withdrawn from the consecrated wafer, the accidents of that substance remained as before, but independent, and not inherent in any other. Arnauld raised this objection, which Descartes endeavoured to repel by a new theory of transubstantiation; but it always left a shade of suspicion, in the Catholic church of Rome, on the orthodoxy of Cartesianism.

of intuitive

104. "The paramount and indisputable authority which, in all our reasonings concerning the human mind, His notions he ascribes to the evidence of consciousness," is truth. reckoned by Stewart among the great merits of Descartes. It is certain that there are truths which we know, as it is called, intuitively, that is, by the mind's immediate inward glance. And reasoning would be interminable, if it did not find its ultimate limit in truths which it cannot prove. Gassendi imputed to Descartes, that, in his fundamental enthymem, Cogito, ergo sum, he supposed a knowledge of the major premise, Quod cogitat, est. But Descartes

replied that it was a great error to believe that our knowledge of particular propositions must always be deduced from universals, according to the rules of logic; whereas, on the contrary, it is by means of our knowledge of particulars that we ascend to generals, though it is true that we descend again from them to infer other particular propositions. It is probable that Gassendi did not make this objection very seriously.

Vol. ii. p. 305. See, too, the passage, quoted above, in his posthumous dialogue.

[Perhaps the best answer might have been, that Cogito, ergo sum, though

thrown into the form of an enthymem, was not meant so much for a logical inference, as an assertion of consciousness. It has been observed, that Cogito is equivalent to Sum cogitans, and involves the

105. Thus the logic of Descartes, using that word for principles that guide our reasoning, was an instrument of defence both against the captiousness of ordinary scepticism, that of the Pyrrhonic school, and against the disputatious dogmatism of those who professed to serve under the banner of Aristotle. He who reposes on his own consciousness, or who recurs to first principles of intuitive knowledge, though he cannot be said to silence his adversary, should have the good sense to be silent himself, which puts equally an end to debate. But so far as we are concerned with the investigation of truth, the Cartesian appeal to our own consciousness, of which Stewart was very fond, just as it is in principle, may end in an assumption of our own prejudices as the standard of belief. Nothing can be truly self-evident but that which a clear, an honest, and an experienced understanding in another man acknowledges to be so.

Treatise on

106. Descartes has left a treatise highly valuable, but not very much known, on the art of logic, or rules art of logic. for the conduct of the understanding. Once only, in a letter, he has alluded to the name of Bacon. There are, perhaps, a few passages in this short tract that remind us of the Novum Organum. But I do not know that the coincidence is such as to warrant a suspicion that he was

conclusion. It is impossible to employ rules of logic upon operations of the mind which are anterior to all reasoning. -1847.]

d M. Cousin has translated and republished two works of Descartes, which had only appeared in Opera Posthuma Cartesii, Amsterdam, 1701. Their authenticity, from external and intrinsic proofs, is out of question. One of these is that mentioned in the text, entitled "Rules for the Direction of the Understanding;" which, though logical in its subject, takes most of its illustrations from mathematics. The other is a dialogue, left imperfect, in which he sustains the metaphysical principles of his philosophy. Of these two little tracts their editor has said, "that they equal in vigour and perhaps surpass in arrangement the Meditations and Discourse on Method. We see in these more unequivocally the main object of Descartes, and the spirit of the revolution which Las created modern philosophy, and placed in the understanding itself the

principle of all certainty, the point of departure for all legitimate inquiry. They might seem written but yesterday, and for the present age." Vol. xi., preface, p. i. I may add to this, that I consider the Rules for the Direction of the Understanding as one of the best works on logic (in the enlarged sense) which I have ever read; more practically useful, perhaps, to young students, than the Novum Organum; and though, as I have said, his illustrations are chiefly mathematical, most of his rules are applicable to the general discipline of the reasoning powers. It occupies little more than one hundred pages, and I think that I am doing a service in recommending it. Many of the rules will, of course, be found in later books; some possibly in earlier. This tract, as well as the dialogue which follows it, is incomplete, a portion being probably lost.

Si quelqu'un de cette humeur vouloit entreprendre d'écrire l'histoire des apparences célestes selon la méthode de Verulamius. Vol. vi. p. 210.