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in producing the deposition of dew on the surface.

"This law of causation, already se amply es tablished, admits, however, of efficient addi tional corroboration in no less than three ways. First, by deduction from the known laws of aqueous vapour when diffused through air or any other gas, and though we have rot ye come to the Deductive Method, we will not omit what is necessary to render this specula tion complete. It is known by direct experi ment that only a limited quantity of water car remain suspended in the state of vapou each degree of temperature, and at this

"But if we expose rough surfaces instead of polished, we sometimes find this law interfered with. Thus, roughened iron, especially if painted over or blackened, becomes dewed sooner than varnished paper: the kind of surface, therefore, has a great influence. Expose, then, the same material in very diversified states as to surface' (that is, employ the Method of Difference to ascertain concomitance of variations), 'and another scale of intensity becomes at once apparent; those sur-maximum grows less and less as the empera faces which part with their heat most readily by radiation, are found to contract dew most copiously.'

The conclusion obtained by this new application of the method is, that cæteris paribus the deposition of dew is also in some proportion to the power of radiating heat; and that the quality of doing this abundantly (or some cause on which that quality depends) is another of the causes which promote the deposition of dew on the substance.

ture diminishes. From this it follows deductively, that if there is already as much vapour suspended as the air will contain at its existing temperature, any lowering of that temperature will cause a portion of the vapour to be condensed, and become water. But, again, we know deductively, from the laws of heat, that the contact of the air with a body colder than itself, will necessarily lower the temperature of the stratum of air immediately applied to its surface; and will therefore cause it to part with a portion of its water, which accordingly will, by the ordinary laws of gravitation or cohesion, attach itself to the surface of the body, thereby constituting dew. This deductive proof, it will have been seen, has the advantage of proving at once causation as well as coexistence; and it has the additional advantage that it also accounts for the exceptions to the occurrence of the phenomenon, the cases ir which, although the body is colder than the air, yet no dew is deposited, by showing that this will necessarily be the case when the air is so under-supplied with aqueous vapour, comparatively to its temperature, that even when somewhat cooled by the contact of the colder body, it can still continue to hold in suspension all the vapour which was previously suspended in it: thus in a very dry summer there are no dews, in a very dry winter no hoar

"Again, the influence ascertained to exist of substance and surface leads us to consider that of texture; and here, again, we are presented on trial with remarkable differences, and with a third scale of intensity, pointing out substances of a close firm texture, such as stones, metals, etc., as unfavourable, but those of a loose one, as cloth, velvet, wool, eiderdown, cotton, etc.,ras eminently favourable to the contraction of dew.' The Method of Concomitant Variations is here, for the third time, had recourse to; and, as before, from necessity, since the texture of no substance is absolutely firm or absolutely loose. Looseness of texture, therefore, or something which is the cause of that quality, is another circumstance which promotes the deposition of dew; but this third cause resolves itself into the first, viz., the quality of resisting the passage of heat: for substances of loose texture are pre-frost. cisely those which are best adapted for clothing, or for impeding the free passage of heat from the skin into the air, so as to allow their outer surfaces to be very cold, while they remain warm within.'


"It thus appears that the instances in which much dew is deposited, which are very various, agree in this, and, so far as we are able to observe, in this only, that they either radiate heat rapidly or conduct it slowly: qualities between which there is no other circumstance of agreement than that by virtue of either, the body tends to lose heat from the surface more rapidly than it can be restored from within. The instances, on the contrary, in which no dew, or but a small quantity of it, is formed, and which are also extremely various, agree (so far as we can observe) in nothing except in not having this same property.

"This doubt we are now able to resolve. We have found that, in every such instance, the substance must be one which, by its own properties or laws, would, if exposed in the ight, become colder than the surrounding air. The coldness, therefore, being accounted for independently of the dew, while it is proved that there is a connection between the two, it must be the dew which depends on the coldness; or, in other words, the coldness is the cause of the dew.

"The second corroboration of the theory is by direct experiment, according to the canon of the Method of Difference. We can, by cooling the surface of any body, find in all cases some temperature (more or less inferior to that of the surrounding air, according to its hygrometric condition) at which dew will begin to be deposited. Here, too, therefore, the causation is directly proved. We can, it is true, accomplish this only on a small scale; but we have ample reason to conclude that the same operation, if conducted in Nature's great laboratory, would equally produce the effect.

"And, finally, even on that great scale we are able to verify the result. The case is one of those rare cases, as we have shown them to be, in which nature works the experiment for us in the same manner in which we ourselves perform it; introducing into the previous state of things a single and perfectly dennite new circumstance, and manifesting the effect so rapidly that there is not time for any other material charge in the pre-existing circumstances. It is observed that dew is never copiously deposited in situations much screened from the open sky, and not at all in a cloudy night; but if the clouds withdraw even for a few minutes, and leave a clear opening, a deposition of deu presently begins, and goes on increasing. Dew formed in tlear inter


vals will often even evaporate again when the | sky becomes thickly overcast. The proof, therefore, is complete, that the presence or absence of an uninterrupted communication with the sky causes the deposition or nondeposition of dew. Now, since a clear sky is nothing but the absence of clouds, and it is a known property of clouds, as of all other bodies between which and any given object nothing intervenes but an elastic fluid, that they tend to raise or keep up the superficial temperature of the object by radiating heat to it, we see at once that the disappearance of clouds will cause he surface to cool; so that Nature in this case produces a change in the antecedent by definite and known means, and the consequent follows accordingly: a natural experiment which satisfies the requisitions of the Method of Difference."


therefore evade the obstacle; and it is here that the last key of nature appears, the Method of Deduction. We quit the study of the actual phenomeron to observe other and simpler cases; we establish their laws, and we connect each with its cause by the ordinary methods of induction. Then, assuming the concurrence of two or of several of these causes, we conclude from their known laws what will be their tota! effect. We next satisfy ourselves as tc whether the actual movement exactly coincides with the movement foretold, and if this is so, we attribute it to the causes from which we have deduced it. Thus, in order to discover the causes of the planetary motions, we seek by simple induction the laws of two causes : first, the force of primitive impulsion in the direction of the tangent; next, an accelerative attracting force. From these inductive laws we deduce by calculation the motion of a body submitted to their combined influence; and satisfying ourselves that the plane. tary motions observed coincide exactly with the predicted movements, we conclude that the two forces in question. are actually the causes of the planetary motions. "To the Deductive Method," says Mill, "the human mind is indebted for its most conspicuous triumphs in the investigation of nature. To it we owe all the theories by which vast and complicated phenomena are embraced under a few simple laws." Our deviations have led us further than the direct path; we have derived efficiency from imperfection.

These four are not all the scientific methods, but they lead up to the rest. They are all linked together, and no one has shown their connection better than Mill. In many cases these processes of isolation are powerless; namely, in those in which the effect, being produced by a concourse of causes, cannot be reduced into its elements. Methods of isolation are then impracticable. We cannot eliminate, and consequently we cannot perform induction. This serious difficulty presents itself in almost all cases of motion, for almost every movement is the effect of a concurrence of forces; and the respective effects of the various forces are found so mixed up in it that we cannot separate them without destroying it, so that it seems impossible to tell what part each force has in the production of the movement. Take a body acted upon by two forces whose directions form an angle it moves along the diagonal; each part, each moment, each position, each element of its movement, is the If we now compare the two methods, combined effect of the two impelling their aptness, function, and provinces, forces. The two effects are so com- we shall find, as in an abstract, the his mingled, that we cannot isolate either tory, divisions, hopes, and limits of of them, and refer it to its source. In human science. The first appears at order to perceive each effect separately the beginning, the second at the end ve should have to consider the move- The first necessarily gained ascend ments apart, that is, to suppress the ency in Bacon's time, and now begins actual movement, and to replace it by to lose it; the second necessarily lost others. Neither the Method of Agree- ascendency in Bacon's time, and now ment, nor of Difference, nor of Resi- begins to regain it. So that science, dues, nor of Concomitant Variations, after having passed from the deductive which are all decomposing and elimi- to the experimental state, is now pass native, can avail against a phenomenon ing from the experimental to the dewhich by its nature excludes all elemi-ductive. Induction has for its provinc nation and decomposition. We must • Mill's Logic, 1. j


phenomena which are capable of being | nature when we shall have deduced decomposed, and on which we can her millions of facts from two or three experiment. Deduction has for its prov-laws.

ognize that induction has nowhere been explained in so complete and pre cise a manner, with such an abundance of fine and just distinctions, with such extensive and exact applications, with such a knowledge of the practical methods and ascertained results of science, with so complete an exclusion of metaphysical principles and arbitrary suppositions, and in a spirit more in conformity with the rigorous procedure of modern experimental science. You asked me just now what English men have effected in philosophy; I answer, the theory of Induction. Mil is the last of that great line of philosophers, which begins at Bacon, and which, through Hobbes, Newton, Locke, Hume, Herschell, is continued down to our own times. They have carried our national spirit into philos ophy; they have been positive and practical; they have not soared above facts; they have not attempted out-of-the way paths; they have cleared the human mind of its illusions, presumptions, and fancies.

ince indecomposable phenomena, or I venture to say that the theory these on which we cannot experiment. which you have just heard is perfect The first is efficacious in physics, chem- I have omitted several of its character istry, zoology, and botany, in the earl-istics, but you have seen enough to rec ier stages of every science, and also whenever phenomena are but slightly complicated, within our reach, capable of being modified by means at our disposal. The second is efficacious in astronomy, in the higher branches of physics, in physiology, history, in the higher grades of every science, whenever phenomena are very complicated, as in animal and social life, or lie beyond our reach, as the motions of the heavenly bodies and the changes of the atmosphere. When the proper method is not employed, science is at a stand-still: when it is employed, science progresses. Here lies the whole secret of its past and its present. If the physical sciences remained stationary till the time of Bacon, it was because men used deduction when they should have used induction. If physiology and the moral sciences are now making slow progress, it is because we employ induction when deduction should be used. It is by deduction, and according to physical and chemical laws, that we shall be enabled to explain physiological phenomena. It is by deduction, and according to mental laws, that we shall be enabled to explain historical phenomena. And that which has become the instrument of these two sciences, it is the object of all the others to employ. All tend to become deductive, and aim at being summed up in certain general propositions, from which the rest may be deduced. The less numerous these propositions are, the more science advances. The fewer suppositions and postulates a science requires, the more perfect it is become. Such a reduction is its final condition. Astronomy, acoustics, optics, present its models; we shall know

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They have employed it in the only direction in which it can act: they only wished to mark out and light up the already well-trodden ways of the progressive sciences. They have not been willing to spend their labor vainly in other than explored and verified paths; they have aided in the great modern work, the discovery of applicable laws; they have contributed, as men of special attainments do, to the increase of man's power. Can you find many philosophers who have done as much?


You will tell me that our philoso pher has clipped his wirgs in order to strengthen his legs. Certainly; and he has acted wisely. Experience limits the career which it opens to us; it has given us our goal, but also var boundaries. We have only to observe the elements of which our experience is

composed, and the facts from which it sets out, to understand that its range is limited. Its nature and its method confine its progress to a few steps. And, in the first place, the ultimate laws of nature cannot be less numerous than the several distinct species of Our sensations. We can easily reduce a movement to another movement, but not the sensation of heat to that of smell, or of color, or of sound, nor either of these to a movement. We ca: easily connect together phenomena of differe: degrees, but not phenomena differing in species. We find distinct sensations at the bottom of all our knowledge, as simple indecomposable elements, separated absolutely one from another, absolutely incapable of being reduced one to another. Let experience do what she will, she cannot suppress these diversities which constitute her foundation. On the other hand, experience, do what she will, cannot escape from the conditions under which


we could explain every thing by them
but we could not explain these them-
selves. Mill says:

originally and no others, or why they are com
"Why these particular natural agents existed
mingled in such and such proportions, and dis
tributed in such and such a manner throughou
space, is a question we cannot answer.
than this: we can discover nothing regular in
the distribution itself; we can reduce it to a
uniformity, to no law. There are no means by
which, from the distribution of these causes or
agents in one part of space, we could conjec
ture whether a similar distribution prevails in

And astronomy, which just now af
forded us the model of a perfect science,
science. We can predict the number-
now affords us an example of a limited
bodies: but we are obliged to assume,
less positions of all the planetary
beside the primitive impulse and its
amount, not only the force of attraction
distances of all the bodies in question.
and its law, but also the masses and
We understand millions of facts, but

she acts. Whatever be her province, it is by means of a hundred facts which is bounded by time and space; the fact we do not comprehend; we arrive at which she observes is limited and in- necessary results, but it is only by fluenced by an infinite number of other means of accidental antecedents; so facts to which she cannot attain. She that if the theory of our universe were is obliged to suppose or recognize some completed there would still remain two primordial condition from whence she great voids: one at the commencestarts, and which she does not explain.tment of the physical world, the other Every problem has its accidental or arbitrary data: we deduce the rest from these, but there is nothing from which these can be deduced. The sun, the earth, the planets, the initial impulse of heavenly bodies, the primitive chemical properties of substances, are such data. If we possessed them all *Mill's Logic, ii. 4.

"There exists in nature a number of Permanent Causes, which have subsisted ever since the human race has been in existence, and for an indefinite and probably an enormous length of time previous. The sun, the earth, and planets, with their various constituents, air, water, and the other distinguishable substances, whether simple or compound, of which nature s made up, are such Permanent Causes. They have existed, and the effects or consequences which they were fitted to produce have taken place (as often as the other conditions of the production met), from the very beginning of our experience. But we can give no account of the origin of the Permanent Čauses themselves."MILL'S Logic, i. 378.

The resolution of the laws of the heavenly motions established the previously unknown ufamate property of a mutual attraction between all bodies: the resolution, so far as it has yet

at the beginning of the moral world;
the one comprising the elements of
being, the other embracing the ele-
ments of experience; one containing
primary sensations, the other primitive
"Our knowledge," says Roy-
proceeded, of the laws of crystallisation, or
chemical composition, electricity, magnetism,
etc., points to various polarities, ultimately in-
herent in the particles of which bodies are com-
posed; the comparative atomic weights of dif-
ferent kinds of bodies were ascertained by re-
solving, into more general laws, the uniformities
observed in the proportions in which substances
combine with one another; and so forth. Thus,
although every resolution of a complex uni-
formity into simpler and more elementary laws
has an apparent tendency to diminish the num-
ber of the ultimate properties, and really does
remove many properties from the list; yet
(since the result of this simplifying process is tr
trace up an ever greater variety of different ef-
fects to the same agents), the further we ad
vance in this direction, the greater number of
distinct properties we are forced to recognise in
one and the same object; the co-existences of
which properties must accordingly be ranked
among the ultimate generalities of nature.”—
MILL'S Logic, ii. 108.

Ibid. i. 378.

er-Collard, "consists in tracing ignorance as far back as possible."

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which we have found to hd universally on our own planet. The uniformity in the succession must be received not as a law of the universe, of events, otherwise called the law of causation, but of that portion of it only which is within the range of our means of sure observation, with

Can we at least affirm that these irreducible data are so only in appearance, and in relation to our mind? Can we say that they have causes, like the de-a reasonable degree of extension to adjacent

rived facts of which they are the causes? Can we conclude that every event, always and everywhere, happens according to laws, and that this little world of ours, so well regulated, is a sort of epitome of the universe? Can we, by aid of the axioms, quit our narrow confines, and affirm any thing of the universe? In no wise; and it is here that Mill pushes his principles to their furthest consequences: for the law which attributes à cause to every event, has to him no other foundation, worth, or scope, than what it derives from experience. It has no inherent necessity; it draws its whole authority from the great number of cases in which we have recognized it to be true; it only sums up a mass of observations; it unites two data, which, considered in themselves, have no intimate connection; it joins antecedents generally to consequents generally, just as the law of gravitation joins a particular antecedent to a particular consequent; it determines a couple, as do all experimental laws, and shares in their uncertainty and in their restrictions. Listen to this bold assertion:

"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 learnt 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 anything 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, theref:re, which warrant us in rejectng 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." Practically, we may trust in so well-established a law; but

"In distant parts of the stellar regions, where the phenomena may be entirely unlike those with which we are acquainted, it would be folly to affirm confidently that this general law prevails, any more than those special ones

• Mill's Logic, ii. 95.

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cases. To extend it further is to make a supposition without evidence, and to which, in the absence of any ground from experience for es timating its degree of probability, it would D idle to attempt to assign any.' We are, then, irrevocably driven back from the infinite; our faculties and our assertions cannot attain to it; we remain confined in a small circle; our mind reaches not beyond its experience; we can establish nc universai and ne


cessary connection between facts; such a connection probably does not even exist. Mill stops here; but certainly, by carrying out his idea to its full extent, we should arrive at the conception of the world as a mere collection of facts; no internal necessity would induce their connection or their existence; they would be simple arbitrary, accidentallyexisting facts. Sometimes, as in our system, they would be found assembled in such a manner as to give rise to reg. ular recurrences; sometimes they would be so assembled that nothing of the sort would occur. Chance, as Democritus taught, would be at the foundation of all things. Laws would be the result of chance, and sometimes we should find them, sometimes not would be with existences as with numbers-decimal fractions, for instance, which, according to the chance of their two primitive factors, sometimes recur regularly, and sometimes not. This is certainly an original and lofty concep tion. It is the final consequence of the primitive and dominant idea, which we have discovered at the beginning of the system, which has transformed the theories of Definition, of Propositions, and of the Syllogism; which has re duced axioms to experimental truths. which has developed and perfected the theory of induction; which has estab lished the goal, the limits, the province, and the methods of science; which everywhere, in nature and in science, has suppressed interior connections; which has replaced the necessary by the accidental; cause by antecedent: and which consists in affirming that • Ibid. ii. 104.

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