Blackwood's Edinburgh Magazine, No. CCCXXXVI. October, 1843. Vol. LIV.. Various
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experienced. Whatever forms a part of all his experience, forms a part also of all his conceptions, and appears to him universal and necessary, though really, for aught he knows, having no existence beyond certain narrow limits. The habit, however, of philosophical analysis, of which it is the surest effect to enable the mind to command, instead of being commanded by, the laws of the merely passive part of its own nature, and which, by showing to us that things are not necessarily connected in fact because their ideas are connected in our minds, is able to loosen innumerable associations which reign despotically over the undisciplined mind; this habit is not without power even over those associations which the philosophical school, of which I have been speaking, regard as connate and instinctive. I am convinced that any one accustomed to abstraction and analysis, who will fairly exert his faculties for the purpose, will, when his imagination has once learned to entertain the notion, find no difficulty in conceiving that in some one, for instance, of the many firmaments into which sidereal astronomy now divides the universe, events may succeed one another at random, without any fixed law; nor can any thing in our experience, or in our mental nature, constitute a sufficient, or indeed any, reason for believing that this is nowhere the case. The grounds, therefore, which warrant us in rejecting such a supposition with respect to any of the phenomena of which we have experience, must be sought elsewhere than in any supposed necessity of our intellectual faculties.
"As was observed in a former place, the belief we entertain in the universality, throughout nature, of the law of cause and effect, is itself an instance of induction; and by no means one of the earliest which any of us, or which mankind in general, can have made. We arrive at this universal law by generalisation from many laws of inferior generality. The generalising propensity which, instinctive or not, is one of the most powerful principles of our nature, does not indeed wait for the period when such a generalisation becomes strictly legitimate. The mere unreasoning propensity to expect what has been often experienced, doubtless led men to believe that every thing had a cause, before they could have conclusive evidence of that truth. But even this cannot be supposed to have happened until many cases of causation, or, in other words, many partial uniformities of sequence, had become familiar. The more obvious of the particular uniformities suggest and prove the general uniformity; and that general uniformity, once established, enables us to prove the remainder of the particular uniformities of which it is made up. * * *
"With respect to the general law of causation, it does appear that there must have been a time when the universal prevalence of that law throughout nature could not have been affirmed in the same confident and unqualified manner as at present. There was a time when many of the phenomena of nature must have appeared altogether capricious and irregular, not governed by any laws, nor steadily consequent upon any causes. Such phenomena, indeed, were commonly, in that early stage of human knowledge, ascribed to the direct intervention of the will of some supernatural being, and therefore still to a cause. This shows the strong tendency of the human mind to ascribe every phenomenon to some cause or other; but it shows also that experience had not, at that time, pointed out any regular order in the occurrence of those particular phenomena, nor proved them to be, as we now know that they are, dependent upon prior phenomena as their proximate causes. There have been sects of philosophers who have admitted what they termed Chance as one of the agents in the order of nature by which certain classes of events were entirely regulated; which could only mean that those events did not occur in any fixed order, or depend upon uniform laws of causation. * * *
"The progress of experience, therefore, has dissipated the doubt which must have rested upon the universality of the law of causation, while there were phenomena which seemed to be sui generis; not subject to the same laws with any other class of phenomena, and not as yet ascertained to have peculiar laws of their own. This great generalisation, however, might reasonably have been, as it in fact was by all great thinkers, acted upon as a probability of the highest order, before there were sufficient grounds for receiving it as a certainty. For, whatever has been found true in innumerable instances, and never found to be false after due examination in any, we are safe in acting upon as universal provisionally, until an undoubted exception appears; provided the nature of the case be such that a real exception could scarcely have escaped our notice. When every phenomenon that we ever knew sufficiently well to be able to answer the question, had a cause on which it was invariably consequent, it was more rational to suppose that our inability to assign the causes of other phenomena arose from our ignorance, than that there were phenomena which were uncaused, and which happened accidentally to be exactly those which we had hitherto had no sufficient opportunity of studying."—Vol. II. p. 108.
Hypotheses.—Mr Mill's observations on the use of hypotheses in scientific investigation, except that they are characterized by his peculiar distinctness and accuracy of thought, do not differ from the views generally entertained by writers on the subject. We are induced to refer to the topic, to point out what seems to us a harsh measure dealt out to the undulatory theory of light—harsh when compared with the reception given to a theory of Laplace, having for its object to account for the origin of the planetary system.
We had occasion to quote a passage from Mr Mill, in which he remarks that the majority of scientific men seem not yet to have completely got over the difficulty of conceiving matter to act (contrary to the old maxim) where it is not; "for though," he says, "they have at last learned to conceive the sun attracting the earth without any intervening fluid, they cannot yet conceive the sun illuminating the earth without some such medium." But it is not only this difficulty (which doubtless, however, is felt) of conceiving the sun illuminating the earth without any medium by which to communicate its influence, which leads to the construction of the hypothesis, either of an undulating ether, or of emitted particles. The analogy of the other senses conducts us almost irresistibly to the imagination of some such medium. The nerves of sense are, apparently, in all cases that we can satisfactorily investigate, affected by contact, by impulse. The nerve of sight itself, we know, when touched or pressed upon, gives out the sensation of light. These reasons, in the first place, conduct us to the supposition of some medium, having immediate communication with the eye; which medium, though we are far from saying that its existence is established, is rendered probable by the explanation it affords of optical phenomena. At the same time it is evident that the hypothesis of an undulating ether, assumes a fluid or some medium, the existence of which cannot be directly ascertained. Thus stands the hypothesis of a luminiferous ether—in what must be allowed to be a very unsatisfactory condition. But a condition, we think, very superior to the astronomical speculation of Laplace, which Mr Mill, after scrutinizing the preceding hypothesis with the utmost strictness, is disposed to treat with singular indulgence.
"The speculation is," we may as well quote throughout Mr Mill's words, "that the atmosphere of the sun originally extended to the present limits of the solar system: from which, by the process of cooling, it has contracted to its present dimensions; and since, by the general principles of mechanics, the rotation of the sun and its accompanying atmosphere must increase as rapidly as its volume diminishes, the increased centrifugal force generated by the more rapid rotation, overbalancing the action of gravitation, would cause the sun to abandon successive rings of vaporous matter, which are supposed to have condensed by cooling, and to have become our planets.
"There is in this theory," Mr Mill proceeds, "no unknown substance introduced upon supposition, nor any unknown property or law ascribed to a known substance. The known laws of matter authorize us to suppose, that a body which is constantly giving out so large an amount of heat as the sun is, must be progressively cooling, and that by the process of cooling it must contract; if, therefore, we endeavour, from the present state of that luminary, to infer its state in a time long past, we must necessarily suppose that its atmosphere extended much further than at present, and we are entitled to suppose that it extended as far as we can trace those effects which it would naturally leave behind it on retiring; and such the planets are. These suppositions being made, it follows from known laws that successive zones of the solar atmosphere would be abandoned; that these would continue to revolve round the sun with the same velocity as when they formed part of his substance, and that they would cool down, long before the sun himself, to any given temperature, and consequently to that at which the greater part of the vaporous matter of which they consisted would become liquid or solid. The known law of gravitation would then cause them to agglomerate in masses, which would assume the shape our planets actually