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the subject, unphilosophical and fanciful at best, even when applied to the sense of seeing, are, in the case of all the other senses, obviously unintelligible and self-contradictory. As to objects of sight, says Dr. Reid, I understand what is meant by an image of their figure in the brain : but how shall we conceive an image of their color, where there is absolute darkness ? And, as to all other objects of sense, except figure and color, I am unable to conceive what is meant by an image of them. Let any man say, what he means by an image of heat and cold, an image of hardness or softness, an image of sound or smell, or taste. The word image, when applied to these objects of sense, has absolutely no meaning. This palpable imperfection in the ideal theory, has plainly taken rise from the natural order in which the phenomena of perception present themselves to the curiosity.
The mistakes, which have been so long current in the world, about this part of the human constitution, will, I hope, justify me for prosecuting the subject a little fartber; in particular, for illustrating at some length, the first of the two general remarks already referred to. This speculation I enter upon the more willingly, that it affords me an opportunity of stating some important principles with respect to the object, and the limits, of philosophical inquiry ; to which I shall frequently have occasion to refer, in the course of the following disquisitions.
Of certain natural Prejudices, which seem to have given rise to the I shall endeavor to show, in another part of this work, that the doctrine I have now stated does not lead to these sceptical conclusions, concerning the existence of a First Cause, which an author
common Theories of Perception. It seems now to be pretty generally agreed among philosophers, that there is no instance in which we are able to perceive a necessary connexion between two successive events; or to comprehend in what manner the one proceeds from the other, as its cause. rience indeed we learn that there are many events, which are constantly conjoined, so that the one invariably follows the other : but it is possible, for anything we know to the contrary, that this connexion, though a constant one, as far as our observation has reached may not be a necessary connexion ; nay, it is possible, that there may be no necessary connexions among any of the phenomena we see: and, if there are any such connexions existing, we may rest assured that we shall never be able to discover them.*
* In consequence of the inferences which Mr. Hume has deduced from this doctrine concerning cause and effect, some later authors have been led to dispute its truth ; not perceiving that the fallacy of this part of Mr. Hume's system does not consist in his premises, but in the conclusion which he draws from ihem.
That the object of the physical inquirer is not to trace necessary connexions, or to ascertain the efficient causes of phenomena, is a principle which has been frequently ascribed to Mr. Hume as its author, both by his followers and by his op
ponents; but it is, in fact, of a much earlier date, and has been maintained by many of the most enlightened, and the least sceptical of our modern philosophers : nor do I know that it was ever suspected to have a dangerous tendency, till the publication of Mr. Hume's writings. “ If we except,” says Dr. Barrow, “the mutual causality and dependence of the terms of a mathematical demonstration, I do not think that there is any other causality in the nature of things, wherein a necessary consequence can be founded. Logicians do indeed boast of I do not know what kind of demonstrations from external causes either efficient or final, but without being able to show one genuine example of any such; nay, I imagine it is impossible for them so to do. For there can be no such connexion of an external efficient cause with its effect, (at least none such can be understood by us,) through which, strictly speaking, the effect is necessarily supposed by the supposition of the efficient cause, or any determinate cause by the supposition of the effect.” He adds afterwards, “ Therefore there can be no argumentation from an efficient cause to the effect, or from an effect to the cause which is lawfully necessary.”—Mathematical Lectures read at Cambridge.
Dr. Butler too, in his discourse on the ignorance of man, has remarked, that “it is in general no more than effects, that the most knowing are acquainted with; for as to causes, they are entirely in the dark as the most ignorant. What are the laws," he continues, “by which matter acts on matter, but certain effects, which some having observed to be frequently repeated, have reduced to general rules?"-Butler's Sermons.
“ The laws of attraction and repulsion,” says Dr. Berkely, " are to be regarded as laws of motion, and these only as rules or methods observed in the productions of natural effects, the efficient and final causes whereof are not of mechanical consideration. Certainly, if the explaining a phenomenon be to assign its proper efficient and final cause, it should seem the mechanical philosophers never explained anything; their province being only to discover the laws of nature; that is, the general rules and method of motion; and to account for particular phenomena, by reducing them under, or showing their conformity to such general rules.” -Siris; or, Philosophical Inquiries concerning the Virtues of Tar Water, p. 108.
“ The words attraction and repulsion may, in compliance with custom, be used where, accurately speaking, motion alone is meant.”—Ibid. p. 114.
“ Attraction cannot produce, and in that sense account, for the phenomena; being itself one of the phenomena produced and to be accounted for.”—Ibid.
“ There is a certain analogy, constancy, and uniformity in the phenomena or appearances of nature, which are a foundation for general rules : and these are a grammar for the understanding of nature, or that series of effects in the visible world, whereby we are enabled to foresee what will come to pass in the natural course of things. Plotinus observes, in his third Ennead, that the art of presaging, is in some sort the reading of natural letters denoting order, and that so far forth as analogy obtains in the universe, there may be vaticination. And in reality, he that foretells the motions of the planets, or the effects of medicines, or the result of chemical or mechanical experiments, may be said to do it by natural vaticination.”—Ibid. p. 120, 121.
“ Instruments, occasions, and signs, occur in, or rather make up, the whole visible course of nature."-Ibid. p. 123.
The following very remarkable passage from Mr. Locke shows clearly that this eminent philosopher considered the connexion between impulse and motion, as a conjunction which we learn from experience only; and not as a consequence deducible from the consideration of impulse, by any reasoning à priori. The passage is the more curious, that it is this particular application of Mr. Hume's doctrine, that has been generally supposed to furnish the strongest objection against it.
" Another idea we have of body, is the power of communicating motion by impulse ; and of our souls, the power of exciting motion by thought. These ideas, the one of body, the other of our minds, every day's experience clearly furnishes us with; but if here again we inquire how this is done, we are equally in the dark. For in the communication of motion by impulse, wherein as much motion
of great ingenuity has attempted to deduce from it. At present, it is sufficient for my purpose to remark; that the word cause is used, both by philosophers and the vulgar, in two senses, which are widely
is lost to one body, as is got to the other, which is the ordinariest case, we can have no other conception, but of the passing of motion out of the one into another; which I think is as obscure and inconceivable, as how our minds move or stop our bodies by thought, which we every moment find they do."
-" The communication of motion by thought, which we ascribe to spirit, is as evident as that of impulse, which we ascribe to body. Constant experience makes us sensible of both of these, though our narrow understandings can com. prehend neither."
-“ To conclude, sensation convinces us, that there are solid extended substances; and reflection, that there are thinking ones: experience assures us of the existence of such beings; and that the one hath a power to move body by impulse, and the other by thought. If we would inquire farther into their nature, causes, and manner, we perceive not the nature of extension clearer than we do of thinking. If we would explain them any farther, one is as easy as the other; and there is no more difficulty to conceive, how a substance we know not, should by thought set body into motion, than how a substance we know not, should by impulse set body into motion."'-Locke, book ii. chap. 23, secs. 28, 29.
It is not, indeed, very easy to reconcile the foregoing observations, which are, in every respect, worthy of the sagacity of this excellent philosopher, with the passage quoted from him in page 44 of this work.
Some of Mr. Hume's reasonings concerning the nature of the connexions among physical events, coincide perfectly with those of Malebranche on the same subject; but they were employed by this last writer to support a very different conclusion.
At a still earlier period Hobbes expressed himself with respect to physical con. nexions, in terms so nearly approaching to Mr. Hume's, that it is difficult to suppose that they did not suggest to him the language which he has employed on that subject. " What we call experience,” he remarks, “is nothing else but remembrance of what antecedents have been followed by what consequents." “No man," he continues, “can have in his mind a conception of the future ; for the future is not yet; but of our conceptions of the past we make a future, or rather call past, future relatively. Thus after a man hath been accustomed to see like antecedents followed by like consequents, whensoever he seeth the like come to pass to anything he had seen before, he looks there should follow it the same that followed then. When a man hath so often observed like antecedents to be fol. lowed by like consequents, that whensoever he seeth the antecedent, he looketh again for the consequent, or when he seeth the consequent, maketh account there hath been the like antecedent, then he calleth both the antecedent and the consequent signs of one another.”—Hobbes' Tripos.
I am doubtful whether I should not add to these authorities that of Lord Bacon, who, although he has no where formally stated the doctrine now under consideration, has plainly taken it for granted in all his reasonings on the method of prosecuting philosophical inquiries; for if we could perceive in any instance the manner in which a cause produces its effect, we should be able to deduce the effect from its cause by reasoning à priori; the impossibility of which he everywhere strongly inculcates. “ Homo naturæ minister et interpres tantum facit et intelligit quan. tum de naturæ ordine re vel mente observaverit; nec amplius scit aut potest." I acknowledge, at the same time, that, from the general scope of Lord Bacon's writings, as well as from some particular expressions in them with regard to causes I am inclined to believe that his metaphysical notions on the subject were not very accurate, and that he was led to perceive the necessity of recurring to observation and experiment in natural philosophy, not from a speculative consideration of our ignorance concerning necessary connexions, but from a conviction founded on a review of the history of science, of the insufficiency of those methods of inquiry which his predecessors had pursued. The notion which the ancients had formed of the object of philosophy, which they conceived to be the investigation of efficient causes, was the principal circumstance which misled them in their researches: and the erroneous opinions of Des Cartes on the same subject frustrated all the efforts of his great and inventive genius in the study of physics. “ Perspicuum est,” says he in one passage, “optimam philosophandi viam nos sequutu
different. When it is said that every change in nature indicates the operation of a cause, the word cause expresses something which is supposed to be necessarily connected with the change; and without which it could not have happened. This may be called the metaphysical meaning of the word; and such causes may be called metaphysical or efficient causes. In natural philosophy, however when we speak of one thing being the cause of another, all that we mean is, that the two are constantly conjoined ; so that when we see the one, we may expect the other. These conjunctions we learn from experience alone ; and without an acquaintance with them, we could not accommodate our conduct to the established course of nature. The causes which are the objects of our investigation in natural philosophy, may, for the sake of distinction, be called physical causes.
I am very ready to acknowledge that this doctrine, concerning the object of natural philosophy, is not altogether agreeable to popular prejudices. When a man, unaccustomed to metaphysical speculations, is told, for the first time, that the science of physics gives us no information concerning the efficient causes of the phenomena about which it is employed, he feels some degree of surprise and mortification. The natural bias of the mind is surely to conceive physical events as somehow linked together; and material substances, as possessed of certain powers and virtues, which fit them to produce particular effects. That we have no reason to believe this to be the case, has been shown in a very particular manner by Mr. Hume, and by other writers; and must, indeed, appear evident to every person, on a moment's reflection. It is a curious question, what gives rise to the prejudice ?
In stating the argument for the existence of the Deity, several modern philosophers have been at pains to illustrate that law of our nature, which leads us to refer every change we perceive in the universe, to the operation of an efficient cause. (See Dr. Reid's Essays on the Intellectual Powers of Man.) This reference is not the result of reasoning, but necessarily accompanies the perception, so as to render it impossible for us to see the change, without feeling a conviction of the operation of some cause by which it was produced ; much in the same manner in which we find it to be impossible to conceive a sensation, without being impressed with a belief of the existence of a sentient being. Hence, I apprehend, it is that when we see two events constantly conjoined, we are led to associate the idea of causation or efficiency, with the former, and to refer to it that power or energy by which the change was produced ; in consequence of which association, we come to consider philosophy as the knowledge of efficient causes ; and lose sight of the operation of mind, in producing the phenomena of nature.It is by an association somewhat similar, that we connect our sensations of color, with the primary qualities of body. A moment's reflection must satisfy any one, that the sensation of color can only reside in a mind; and yet our natural bias is surely to connect color with extension and figure, and to conceive white, blue, and yellow, as something spread over the surfaces of bodies. In the same way, we are led to associate with inanimate matter, the ideas of power, force, energy, and causation ; which are all attributes of mind, and can exist in a mind only.
ros, si ex ipsius Dei cognitione rerum ab eo creatarum cognitionem deducere cone. mur, ut ita scientiam perfectissimam quæ est effectuum per causas acquiramus.'
The strong prejudice which has been entertained of late against Mr. Hume's doctrine concerning the connexion among physical events, in consequence of the dangerous conclusions to which it has erroneously been supposed to lead, will, I hope, be a sufficient apology for multiplying so many authorities in support of it.
* There is, I believe, reason to doubt if Des Cartes had ever read the works of Bacon.
The bias of our nature is strengthened by another association.Our language, with respect to cause and effect, is borrowed by analogy from material objects. Some of these we see scattered about us, without any connexion between them ; so that one of them may be removed from its place, without disturbing the rest. We can, however, by means of some material vinculum, connect two or more objects together; so that whenever the one is moved, the others shall follow. In like manner, we see some events, which occasionally follow one another, and which are occasionally disjoined; we see others, where the succession is constant and invariable. The former we conceive to be analogous to objects which are loose, and unconnected with each other, and whose contiguity in place, is owing merely to accidental position; the others, to objects which are tied together by a material vinculum. Hence we transfer to such events, the same language which we apply to connected objects. We speak of a connexion between two events, and of a chain of causes and effects.*
That this language is merely analogical, and that we know nothing of physical events, but the laws which regulate their succession, must, I think, appear very obvious to every person who takes the trouble to reflect on the subject; and yet it is certain, that it has misled the greater part of philosophers; and has had a surprising influence on the systems, which they have formed in very different departments of science.
* This language has ever been adopted by philosophers, and by atheists as well as theists. The latter have represented natural events as parts of a great chain, the highest link of which is supported by the Deity. The former have pretended that there is no absurdity in supposing the number of links to be infinite. Mr. Hlume had the merit of showing clearly to philosophers, that our common language, with respect to cause and effect, is merely analogical; and that if there be any links among physical events, they must forever remain invisible to us. If this part of his system be admitted ; and if, at the same time, we admit the authority of that principle of the mind which leads us to refer every change to an efficient cause ; Mr. Hume's doctrine seems to be more favorable to theism than even the common notions upon this subject; as it keeps the Deity always in view, not only as the first, but as the constantly operating efficient cause in nature, and as the great connecting principle among all the various phenomena which we observe. This, accordingly, was the conclusion which Malebranche deduced from premises very nearly the same with Mr. II ume's.