One source of the general fallacy unquestionably is that influence of abstraction, to which I before alluded, as aided, and in a great measure perpetuated, by the use of language, and the common unavoidable modes of grammatical construction. We speak of the powers of a substance, of substances that have certain power – of the figure of a body, or of bodies that have a certain figure, in the same manner as we speak of the students of a university, or of a house that has a great number of lodgers; and we thus learn to consider the power, which a substance possesses, as something different from the substance itself, inherent in it indeed, but inherent, as something that may yet subsist separately. In the ancient philosophy, this error extended to the notions both of form and power. In the case of form, however, we have seen, that the illusion, though it lasted for many ages, did at length cease, and that no one now regards the figure of a body, as any thing but the body itself. It is probable that the illusion, with respect to power, as something different from the substance that is said to possess it, would, in like manner, have ceased, and given place to juster views, if it had not been for the cause, which I am next to consider.
This cause is the imperfection of our senses, the same cause which, in the other department of physics before examined by us, – the department, that relates to matter considered merely as existing in space, – we find to give occasion to all our inquiries into the compositions of bodies. In this department of physics, however, which relates to the successions of phenomena in time, the imperfection of our senses operates in a different way. It is not that which gives occasion to the necessity of inquiry; for we have seen, that senses, of the utmost accuracy and delicacy, could not, of themselves, and without experience, have enabled us to predict any one event, in the innumerable series of phenomena that are constantly taking place around us. But, though senses of the nicest discrimination could not have rendered inquiry into the successions of events superfluous, they would have saved us from much idle inquiry, and have given far greater precision, if not to our rules, at least to our uniform practice, of philosophizing.
As our senses are at present constituted, they are too imperfect, to enable us to distinguish all the elements, that co-exist in bodies, and of elements, which are themselves unknown to us, the minute changes which take place in them, must of course be unknown. We are hence, from our incapacity of discovering these elements by our imperfect senses, and imperfect analysis, incapable of distinguishing the whole series of external changes that occur in them, – the whole progressive series of antecedents and consequents in a phenomenon that appears to our senses simple; and, since it is only between immediate antecedents and consequents, that we suppose any permanent and invariable relation, we are therefore constantly on the watch, to detect, in the more obvious changes that appear to us in nature, some of those minuter elementary changes, which we suspect to intervene. These minute invisible changes, when actually intervening, are truly what connect the obvious antecedents with the obvious consequents; and the innumerable discoveries, which we are constantly making of these, lead us habitually to suppose, that, amid all the visible changes perceived by us, there is something latent which links them together. He who for the first time listens to the delightful sounds of a violin, if he be ignorant of the theory of sound, will very naturally suppose that the touch of the strings by the bow is the cause of the melody which he hears. He learns, however, that this primary impulse would be of little effect, were it not for the vibrations excited by it in the violin itself; and another discovery, still more important, shews him that the vibration of the instrument would be of no effect, if it were not for the elastic medium, interposed, between his ear and it. It is no longer to the violin, therefore, that he looks, as the direct cause of the sensation of sound, but to the vibrating air; nor will even this be long considered by him as the cause, if he turns his attention to the structure of the organ of hearing. He will then trace effect after effect, through a long series of complex and very wonderful parts, till he arrive at the auditory nerve, and the whole mass of the brain, – in some unknown state of which he is at length forced to rest, as the cause or immediate antecedent, of that affection of the mind, which constitutes the particular sensation. To inquire into the latent causes of events is thus to endeavour to observe changes which we suppose to be actually taking place before us unobserved, very nearly in the same manner, as to inquire into the composition of a substance is to strive to discover the bodies that are constantly before us, without our being able to distinguish them.
It is quite impossible, that this constant search, and frequent detection of causes, before unknown, thus found to intervene between all the phenomena observed by us, should not, by the influence of the common principles of our mental constitution, at length associate, almost indissolubly, with the very notion of changes as perceived by us, the notion of something intermediate, that as yet lies hid from our search, and connects the parts of the series which we at present perceive. This latent something, supposed to intervene between the observed antecedent and the observed consequent, being the more immediate antecedent of the change which we observe, is of course regarded by us as the true cause of the change, while the antecedent actually observed by us, and known, ceases, for the same reason, to be regarded as the cause, and a cause is hence supposed by us, to be something very mysterious; since we give the name, in our imagination, to something of the nature of which we must be absolutely ignorant, as we are, by supposition, ignorant of its very existence. The parts of a series of changes, which we truly observe, are regarded by us as little more than signs of other intervening changes as yet undetected; and our thought is thus constantly turned from the known to the unknown, as often as we think of discovering a cause.
The expectation of discovering something intermediate and unknown between all known events, it thus appears, is very readily convertible into the common notion of power, as a secret and invisible tie. Why does it do this? or, How does it produce this effect? is the question which we are constantly disposed to put, when we are told of any change which one substance occasions in another; and the common answer, in all such cases, is nothing more than the statement of some intervening object, or event, supposed to be unknown to the asker, but as truly a mere antecedent in the sequence, as the more obvious antecedent which he is supposed to know. How is it that we see objects at a distance – a tower, for example, on the summit of a hill, on the opposite side of a river? Because rays of light are reflected from the tower to the eye. The new antecedent appears to us a very intelligible reason. And why do rays of light, that fall in confusion from every body, within our sphere of vision, on every point of the surface of the eye, – from the wood, the rock, the bridge, the river, as well as the tower, – give distinct impressions of all these different objects? Because the eye is formed of such refracting power, that the rays of light, which fall confusedly on its surface, converge within it, and form distinct images of the objects from which they come, on that part of the eye which is an expansion of the nerve of sight. Again we are told only of intervening events before unknown to us; and again we consider the mere knowledge of these new antecedents as a very intelligible explanation of the event which we knew before. This constant statement of something intermediate, that is supposed to be unknown to us, as the cause of the phenomena which we perceive, whenever we ask, how or why they take place? continually strengthens the illusion, which leads us to regard the powers of objects as something different from the perceived objects themselves; – and yet it is evident, that to state intervening changes, is only to state other antecedents, – not any thing different from mere antecedence, – and that whatever number of these intervening changes we may discover between the antecedent and the consequent, which we at present know, we must at length come to some ultimate change, which is truly and immediately antecedent to the known effect. We may say, that an orator, when he declaims, excites the sensation of sound, because the motion of his vocal organs excites vibrations in the intervening air, – that these vibrations of air are the cause of the sound, by communicating vibration to parts of the ear, and that the vibrations of these parts of the ear are the cause of the sound, by affecting in a particular manner the nerve of hearing, and the brain in general; – but, when we come to the ultimate affection of the sensorial organ, which immediately precedes the sensation of the mind, it is evident, that we cannot say of it, that it is the cause of the sound, by exciting any thing intermediate, since it then could not itself be that by which the sound was immediately preceded. It is the cause, however; exactly in the same manner as all the other parts of the sequence were causes, merely by