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planetary system, he traces order, and in its perpetual fluctuations the principle of stability and security.
Physical analogies are not only allowable helps to the interpretation of nature, but they are the sole legitimate guides. The philosopher is not merely at liberty to adopt them as convenient aids, but he is driven by the necessity of the case to follow them. He has no other means of ever arriving at an acquaintance with the scheme of natural causes. Their reality alone constitutes what we mean by such order. It is the uniformity actually found in certain limited portions of nature which leads to the presumption of its universality. But it is under the guidance of that presumption that every step of physical inquiry proceeds: and the universal confirmation of it is the general conclusion of all our researches. And the further sound induction extends, the more does every fresh inference add force to the claims of some high principle of order to be recognised as pervading all nature. That induction can go on satisfactorily and successfully in every new region of inquiry which may be opened to it, is of itself a proof of the permanence and universality of such order and system.
Upon the foregoing considerations we may, perhaps, more correctly appreciate the standard of evidence to which sound physical philosophy appeals; and the importance of a clear perception of real physical analogies in the study of it. We have, however, already remarked at once the difficulty of explaining the weight which those analogies possess, yet, at the same time, the actually irresistible force with which they impress the mind. And if the evidence be thus in any degree open to difference in its application to different minds, what does this amount to but saying that inductive proof does not amount to demonstration; or, more correctly, is proof of a different kind. But at any rate if it be allowed that there has been no attempt to overrate the evidence, this will but give additional security to the important inferences and applications to which we shall advance.
Study of Cause and Effect. The more special object of the preceding section has been to examine the nature and principles of the Inductive Method, the characteristic process of the Baconian philosophy. Now the principal aim and object of this system is to ascend from individual phenomena to general laws; from sensible and visible results, up to hidden and abstract principles ; from the experimental evidence of sense, up to the abstractions of mind; from effects, to their causes.
In the present instance it is proposed to carry on the subject by the further examination of the nature of the relation of cause and effect, and this, more especially in the first instance, with reference to the
causes which we trace in operation in the material world. The evidence on which our knowledge of these causes depends is that afforded by induction, which we have already been engaged in tracing ; and in proceeding, as we are now about to do, to the more direct consideration of their nature, we shall find that this discussion has not been misplaced; and that, in fact, in studying the evidence, we have arrived at some of the most important observations for bringing us to the apprehension of the nature of physical causes. In tracing the essential grounds of induction, it will be found that we have elicited what will be our safest guide in the inquiry into the principle of causation.
From the earliest periods at which intellectual pursuits have attained anything like a due place in the estimation of mankind, a high rank has always been assigned to the study of the causes of things. Surrounded as we are by the most stupendous scene of natural wonders, it would indeed be surprising if the curiosity of man were not excited, even in an early stage of civilization, to learn something of the nature and source of those effects which he daily witnesses in the magnificent phenomena of the material world. And we accordingly find that from the earliest times at which the human race has been sufficiently advanced to give attention to such subjects, the inquiry into the nature and relations, the dependence and connexion, of natural phenomena, has obtained at least some share of attention; and though pursued only by a few, has conferred upon them, at all times, à certain degree of reputation even among the uninstructed, while with those of more enlightened ideas, a knowledge of the causes of those effects which we daily witness has been regarded as among the highest objects of intellectual attainment; and to be permitted thus to penetrate, as it were, into the hidden processes by which nature works, has been esteemed the most elevated privilege of philosophy. It is a species of knowledge of extreme interest and value in itself, and embraces in its applications, some of the most important and even momentous questions which can occupy human contemplation.
Meaning of the term “ Cause."
In order to pursue our inquiry into the nature of Physical Causes, it will be essential, in the first instance, to distinguish, as clearly as we can, the meaning annexed to the term.
In common language, the term “cause” is used with considerable latitude of meaning; and even in many discussions pretending to a philosophic character, a slight examination will show that it bears several distinct kinds of signification. We are apt to use the same word, and thence imagine that we are speaking of the same thing, in cases which are essentially different; though there is doubtless enough of apparent resemblance to mislead inaccu
rate thinkers into the notion of identity. Hence the ambiguity and fallacy which prevail in some of the most important inquiries connected with this subject; and the manifest necessity for attention to accurate distinction of the meaning of terms.
In ordinary affairs, we talk of the “ cause” of an undertaking, or the “ cause” of our conduct. Again we speak of the “ cause” of an historical event; and we apply the term to matters of reasoning or belief in the conjunction “ because.” We mean the motive of our actions; the ground or evidence of our opinion; the train of circumstances which brought about an event in history. In these and the like cases, we may trace a general analogy, which has led to the application of the same term. In all of them we refer to some sort of moral influence exercised either by concurrent circumstances upon human motives or convictions, or by human agency (individual or collective) upon events.
In the discussion of causes and effects, as we contemplate them in the natural world, and in connexion with physical science, it is more especially necessary to guard against the vague use of terms. And in proceeding to the more precise examination of the nature of physical causes, we may conside more particularly, as a preliminary illustration in the way of contrast, two familiar instances of the use of the term “ cause."
We may say the cause of the motions of a watch is the tendency of the main-spring to unwind itself;