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and the cause of the flight of the cricket-ball is the voluntary effort of the player. These are two instances which would seem, at first sight, closely to resemble each other; but when accurately examined, we find an important distinction between them. In the /ormer instance, we trace the order of dependence of the motions from the index to the wheels, from the wheels to the fusee, and so up to the tendency of the spring to unwind; and this we refer to the property of elasticity; which again may possibly depend on some still higher principle in the nature and arrangement of the particles of which elastic bodies are composed. But to whatever extent we may advance in thus analyzing the effect up to its simplest elements, one thing is all along manifest; viz., that the very highest principle of any such series must essentially be some general, fixed, inherent, property of matter; by virtue of which it is capable of being influenced in particular ways, and by particular agents; but yet is wholly inert, and incapable of arbitrarily originating any of the effects referred to.
In the second case, we may observe, it is true, a like series of effects in succession dependent one on another. Motion is communicated mechanically to the ball from the sudden action of the arm; this results from the contraction of the muscles acting on the bones as levers; the muscular contraction again may be shown to depend on some peculiar influence of the nerves; this again may possibly be traced to some higher principle; we may advance, in short, as far as physiological science can carry us; and thus far, this and the former case are exactly alike. But here at the commencement of the whole train, there must still be an influence or cause of some kind different from any mechanical power; depending on voluntary agency; capable of originating the series of consequences from itself; acting by different laws from those of matter; in a word, an agency or influence of a moral kind: Or (in the graphic language of Sir J. Herschel*), we must include "a distinct and immediate personal consciousness of causation in the enumeration of that sequence of events by which the volition of the mind is made to terminate in the motion of material objects; I mean the consciousness of effort, as a thing entirely distinct from mere desire or volition on the one hand, and from mere spasmodic contraction of the muscles on the other."
Such a voluntary agency, such an influence or power, of which we feel conscious, and which implies the action (however incomprehensible,) of mind on matter, is what we may properly distinguish by the term "moral causation." The former case we may call, by way of contradistinction, an instance of " physical causation." In the study of causes acting in the natural world, we must care
* Astronomy, p. 232.
fully observe this distinction. Cases where voluntary or moral agency is concerned, can only be considered in physical inquiry so far as they properly come under the laws of inert matter, or belong to those kinds of physical action which are the subjects of dynamical or chemical research. To go beyond this is to confound physical causes with moral, physical science with metaphysical.
Observing this distinction, it would no doubt tend much to the promotion of accurate views if we could succeed in agreeing to disuse the term "cause" in one or other of these very distinct cases. But as custom has probably established the use of the term beyond the possibility of change, we must content ourselves by insisting strongly on the careful and constant adoption of some such distinctive appellations as those above suggested.
We have thus far merely contended that physical causes are such as are widely distinguished from moral; but we have not yet considered what their essential nature is: to this we now proceed.
Nature of Physical Causes.
In the study of physical causes there has been, doubtless, and still exists, a strong tendency to lose sight of the distinction just laid down; and from the familiar notion of moral causation, to imagine a similar sort of influence in the production of physical effects: to transfer the idea of voluntary power as experienced in ourselves to mechanical agents; and by a creation of the fancy, by a sort of personification of the powers of nature, to invest physical, with the attributes of moral, action. But such indulgence of the imagination is here worse than idle; it has a direct tendency to confuse and entangle the chain of reasoning; and this consideration becomes of more importance in reference to the conclusions founded on physical inquiry. On all grounds, then, we ought surely to keep the search into physical truth as free as possible from such incongruous influence; and soberly investigate physical causes without being misled by the adoption of ideas so foreign to the subject.
Yet notions more or less allied to these have been prevalent among philosophers. This propensity for physical mysticism was pre-eminently fostered in the labyrinths of the scholastic and Cartesian systems of a past age. But the traces of it have not yet been wholly or effectually banished from our schools of science.
Even in later times many philosophers have sought to establish the notion of what they termed a " necessary connexion" or " efficient causation" in natural phenomena; an idea which nevertheless it would appear very difficult distinctly to explain.
It would seem as if they regarded material substances as possessed of some hidden virtues or properties, which confer on them the powers of physical agents; and imagined these occult qualities the
secret soul which animates, as it were, the whole frame of nature.
In some instances, the adoption of these ideas may be traced to associations arising out of the common use of metaphorical language*. We talk of the chain of cause and effect; the links of that chain ; the connexion of one event with another; the dependence of causes; the production of a result from its cause. These metaphors being taken from material objects, insensibly lead many minds to suppose some similar, real, and effective union between the events. But this is nothing more than the very common mistake of straining a metaphor beyond the points of parallelism, in which it properly applies, to others which are wholly incidental. Perhaps we might rather say these metaphors themselves have been adopted and conceived upon a false train of analogy. At any rate, if we retain the use of them, we should be careful not to be misled by the phraseology we employ into ideas at variance with the real nature of the relation intended to be expressed by it.
Another source, perhaps, from which these notions of " efficient causation" have derived strength, may be discovered in the vague conceptions which have sometimes prevailed with regard to the nature of mechanical forces. We might instance some speculations on the nature of " inertia," and the commu