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et Planetarum, sine virtutis diminutione; quæque agit non pro quantitate superficierum particularium in quas agit, (ut solent causæ mechanicæ) sed pro quantitate materiæ solidæ; et cujus actio in immensas distentias undique extenditur, decrescendo semper in duplici ratione distantiarum. Rationem vero harum gravitatis proprietatum ex phænomenis nondum potui deducere, et hypotheses non fingo. *"
* The English reader will find the above passages of Newton thus transJated by Dr. Clarke in his fifth reply to Leibnitz.
What the efficient cause of these attractions is, I do not here inquire. What I call attraction may possibly be caused by some impulse or some other way unknown to us. I use the word attraction only in general to sigoify the force by which bodies tend towards each other, whatever may be the cause of that force. For we must learn from the phenomena of nature, what bodies attract each other, and what are the laws and properties of that attraction, before it be proper to inquire what the efficient cause of attraction is. Agaio- I consider these principles not as occult qualities, imagined to arise from the specific forms of things; but as universal laws of nature, according to which the things themselves were formed. For that such principles do really exist, appears from the phenomena of pature, though what the causes of them are, be not yet explained. To affirm that every distinct species of things, is endued with specific occult qualities, by means whereof the things have certain active powers, this, indeed, is doing nothing. But to deduce from the phenomena of nature, two or three general principles of motion, and then to explain how the properties and actions of all coporeal things follow from these principles; this would be a great progress in philosophy, though the causes of those principles were not yet discovered. Again—I have explained the phenomena of the Heavens and the sea by the force of gravity; but the cause of gravity I have not yet assigned. It is a force arising from some cause which reaches to the very centre of the sun and planets, without any diminution of its force, and it acts not proportionally to the surfaces of the parLicles it acts upon, as mechanical causes use to do, but proportionally to the quantity of solid matter. And its action reaches every way to immense distances, decreasing always in a duplicate ratio of the distances. But the cause of these properties of gravity, I have not yet found deducible from the phenomena, and bypotheses I frame not.
We have selected these passages from the works of Newton, because, taken together, they furnish sufficiently clear and exact ideas about the signification of those terms whose explanation we have attempted. First, the cause or great operating principle of gravity whose influence pervades the whole system, reaching to the very centre of the planets and the sun, he acknowledges to be unknown, not yet appearing to him to be deducible from the phenomena. Next, the laws of gravitation, or the rules by which the unknown principle operates, he considers as ascertained by observation and just inference of reason; and lastly the facts or phenomena themselves are the tendencies of all bodies around the earth to its centre, and the motions of the heavenly bodies. These are precisely the views of these matters which we have endeavoured to establish, The opinions of Bacon, Des Cartes, and unnumbered other philosophers might easily be shown to correspond with these,
The opinions of Mr. Hume on Cause and Effect.
Such a full and elaborate explanation of terms, in themselves simple and intelligible, would have been unnecessary, had they not been rendered ambiguous and confused in their signification by some writers of a more recent date than the authors before referred to. That writers, whose evident aim is, to treat every received maxim in science as a professed enemy, with whom they are to wage hostility, and who, in the prosecution of this warfare, would unsettle the foundations, not only of religious and moral, but even of philosophical and mathematical truth, and conduct the understandings of mankind to universal scepticism, and even a blank atheism, should adopt as one of the expedients, by which to accomplish their purpose, a doubtful and cloudy application of terms; sometimes, taking them as expressive of one combination of ideas, and, at other times, of another; at one time, using them according to ordinary acceptation, at another, in a meaning variant from the authorised usage of the language, was to have been anticipated. Accordingly we find Mr, Hume, in his treatise of human nature, giving the following account of cause and effect, as far as his opinion is to be collected from the affected obscurity of his style, and the studied intricacy and involution in his modes of thinking. He divides all our perceptions into impressions and ideas, the latter being regarded merely as the faint images or copies of the former; and to this arbitrary division of our perceptions, alike unknown to the schools and to nature, he adverts in laying the foundation of his doctrine about causation. “To begin regularly,” says he, “ we must consider the idea of causation, and see from what origin it is derived. 'Tis impossible to reason justly without understanding perfectly the idea concerning which we reason; and 'tis impossible perfectly to understand any idea without tracing it up to its origin, and examining that primary impression from which it arises. Let us, therefore, cast our eyes on any two objects which we call cause and effect, and turn them on all sides in order to find that impression which produces an idea of such prodigious consequence.” He maintains that, with the most diligent search, he can discover no previous impression, from which the idea of efficiency or necessary connection between causes and effects can be derived, and that the relation of contiguity and constant conjunction are all that are essential to causation. But lest it should be asserted that our having a distinct idea of force, power or efficiency in one object to produce an effect upon another, shows that we have some ideas which have not been preceded by their correspondent impression, and overthrows his theory of perception, instead of his theory overturning the doctrine of causation; he proceeds to the discussion of the two following propositions. “ First, for what reason we pronounce it necessary, that every thing whose existence has a beginning, shuuld also have a cause? Secondly, why we conclude thai such particular causes must necessarily have such particular effects?” In reference to that maxim so generally received in philosophy, that whatever begins to exist must have a cause of its existence, it is neither intuitively nor demonstrably certain. And since it is not from knowledge or scientific reasoning, that we derive the opinion of the necessity of a cause to every new production, that opinion must necessarily arise from experience and observation. Now the nature of experience is this. We remember to have had frequent instances of the existence of one species of objects; and also remember that the indivi. duals of another species of objects have always attended them, and have existed in regular order of contiguity and succession in regard to them. Thus we remember to have seen that species of objects we call flame, and to have felt that
species of sensation we call heat. We likewise call to mind their constant conjunction in all past instances. Without any further ceremony we call the one cause and the other effect, and infer the existence of the one from that of the other. In giving a solution of the second question, viz. why we conclude that such particular causes must have such particular effects, he maintains; “ that if it be allowed for a moment, that the production of one object by another in any one instance implies a power, and that this power is connected with the effect, we have no reason to infer that the same power still exists merely upon the appearance of the sensible qualities. The appeal to past experience decides nothing; and at the very utmost can only prove that that very object which produced any other, was at that very instant, endowed with such a power, but can never prove that the same power must continue in the same object or collection of sensible qualities; much less that a like power is always conjoined to such sensible qualities. Thus," he concludes,“ not only our reason fails us in the discovery of the ultimate connexion between causes and effects; but even after experience has informed us of their constant conjunction; ʼtis impossible for us to satisfy ourselves by our reason why we should extend that experience beyond those particular instances which have fallen under our observation.”
The passages before extracted from Locke, Newton and Cicero, when compared to these from Mr. Hume upon the same subject, furnish us with a tolerably just conception of the difference between that clear and intense light which is shed around the investigations of the true philosopher, of him who exerts himself to the utmost to become, in sincerity and truth, the faithful interpreter of nature; and those faint and false fires which cast a dubious and deceptive glimmering along the footsteps of those who would sedulously, and with full purpose of mischief, lead us astray from the paths of truth and right reason. Is there any one who is in the smal