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nication of motion; as well as others connected with the questions once agitated respecting the “ vis viva.” Or, to take a more familiar example, the indistinct notions which frequently involve in a singular degree of mystery, the advantage obtained in the use of the mechanical powers. On witnessing the effects produced by these contrivances, the untaught mind can hardly help imagining a sort of creative energy which invests matter with new attributes, and supplies a source of active power capable of almost indefinite increase. Scientific investigation, indeed, dispels the illusion, yet it often continues to baunt both our language and our ideas relative to the nature of causation.
Opinions on the Nature of Causation.
WHETHER, however, originating in such misconceptions or not, whether pushed to a greater or less extent, some notions of this kind have prevailed very generally. But reasoners of an opposite school have arisen, who, aiming at a peculiar degree of precision and rigour in their speculations, have utterly denied and discarded all ideas of such active, efficient influence, which, they contend, is altogether chimerical; and have sought to reduce the whole nature and conception of cause and effect to the bare, naked, matter-of-fact, learnt from experience, that some one particular event or phenomenon in nature always invariably follows another in order of
time; the former being termed the effect, the latter the cause; that besides this mere invariable “ sequence” (as it is termed), they have no other kind of connexion or dependence one on the other; all we know or can know of the matter is the simple fact, that such sequence does universally hold good; and that we cannot reverse the order.
If we be prone to entertain the idea of any higher or more intimate connexion, this, they contend, is only a vague prepossession, utterly inadmissible in exact philosophic inquiry.
Against these views considerable objection has been raised; often, doubtless, from the abuse of them; because they were too exclusively dwelt upon, or pushed to unwarrantable extremes in their application.
But apart from these objections, the generality of inquirers seem to have felt unable to rest satisfied in a view of the subject apparently so little calculated to gratify the cravings of our intellectual curiosity, and seeming to conduct us to so little an extent into the secret workings of nature which we are so desirous to penetrate. They have generally yielded to the seemingly more natural but vague persuasion, that there is yet in the relation of cause and effect, some real, hidden, essential energy, which pervades and actuates all the operations of the material world.
And some, even of the most truly philosophic minds, have been unwilling wholly to acquiesce in
reducing the notion of causes to what has appeared to them the barren and unsatisfactory relation of a mere invariable junction and sequence of facts; they have been unable to divest themselves wholly of some sort of idea of one event actively occasioning another, and not merely passively preceding it; of an influence of some kind, an intimate connexion, an efficient agency, beyond the bare constancy of a
sequence” or invariable law*.
Physical Causes.—“ Sequence” of Phenomena.
Is, then, physical causation really nothing more than the bare invariable sequence of two facts? To treat the subject fairly, we must of course dismiss, in the first instance, a number of cases which have been often urged against this doctrine, but which the slightest reflection shows to be either frivolous or inapplicable; some such instances are not real invariable sequences of one phenomenon after another; others involve the fallacy of the logician's “ non causa pro causâ;" others are mere statements of the co-existence of two constant properties.
We restrict our view of cause and effect to cases in which some change, either in properties, or in relation or position, occurs; that is, where either some chemical effect or some mechanical motion is produced. To take one or two simple instances of what are properly physical causes and effects : we
* See Note C.
“ friction is a cause of heat:" “ the action of an acid is the cause of a vegetable blue turning red.” The ancients (ignorant of gravitation) considered “ the moon to be the cause of the tides."
In such cases as these there is clearly the invariable association of one fact with another, by a sequence in order of time. Thus, whenever we rub two substances together, under all circumstances, the effect of heat follows; and in greater intensity as the friction is more violent: it depends on this and on this alone. In the strict use of terms, then, in this and the like cases, our proposition is nothing more than the affirmation of this invariable relation of sequence, as a result of universal experience.
In these instances, then, we have a precise exemplification of the doctrine of invariable sequence constituting the whole nature of cause and effect. We observe only such an inseparable relation between the two facts. We may doubtless imagine some higher principle, to account for the production of heat in the one case, and of colour in the other, as the ancients might have imagined (and, perhaps, did so) a sort of principle of attraction in the tides : but whatever we may imagine, we know nothing. When these and the like cases, then, are contemplated in a strictly inductive point of view, we are obliged to admit that nothing is actually proved beyond the invariable “ sequence.”
Causes referred to General Laws : Examples.
A DIFFERENCE may, perhaps, be traced between such instances as these last referred to, and some others which we may adduce. For instance, when we say that “pulsations of air are the cause of sound,” it will be immediately felt that some relation, of a kind more satisfactory to our minds, is here affirmed than in the former cases. There is manifestly an invariable sequence; whenever this sort of pulsation is produced, sound invariably follows, and never without it.
But besides this, the propagation of tremulous waves, or pulsations, through the air is a mechanical effect, of which we form a general idea apart from its influence on our organs; and we refer the vibrations produced in the membranes of our ears, and the sensation which ensues, as a particular case, to the more general fact of pulsations of elastic media. Here, then, there is not only the sequence of one fact upon another, but, also, the former is more comprehensive, and includes the latter as a particular case of a more general class of phenomena.
In the same manner, we say that rapid chemical combination is the cause of that evolution of heat and light which we call combustion.
Here, again, we refer the particular effect to a cause of a more comprehensive kind : what we mean to affirm is, that combustion is a peculiarly rapid and intense species of chemical combination. Again, when we extend the bare matter-of-fact connexion