41. The sight is the noblest of our senses, and if they had been given us to discover truth, it is through vision that we should have done it. But it deceives us in all it represents, in the size of bodies, their figures and motions, in light and colours. None of these are such as they appear, as he proves by many obvious instances. Thus, we measure the velocity of motion by duration of time and extent of space; but of duration the mind can form no just estimate, and the eye cannot determine equality of spaces. The diameter of the moon is greater by measurement when she is high in the heavens; it appears greater to our eyes in the horizon.[792] On all sides we are beset with error through our senses. Not that the sensations themselves, properly speaking, deceive us. We are not deceived in supposing that we see an orb of light before the sun has risen above the horizon, but in supposing that what we see is the sun itself. Were we even delirious, we should see and feel what our senses present to us, though our judgment as to its reality would be erroneous. And this judgment we may withhold by assenting to nothing without perfect certainty.
[792] L. i., c. 9. Malebranche was engaged afterwards in a controversy with Regis on this particular question of the horizontal moon.
42. It would have been impossible for a man endowed with such intrepidity and acuteness as Malebranche to overlook the question, so naturally raised by this sceptical theory, as to the objective existence of an external world. There is no necessary connection, he observes, between the presence of an idea in the soul, and the existence of the thing which it represents, as dreams and delirium prove. Yet we may be confident that extension, figure, and movement, do generally exist without us when we perceive them. These are not imaginary; we are not deceived in believing their reality, though it is very difficult to prove it. But it is far otherwise with colours, smells, or sounds, for these do not exist at all beyond the mind. This he proceeds to show at considerable length.[793] In one of the illustrations subsequently written in order to obviate objections, and subjoined to the Recherche de la Vérité, Malebranche comes again to this problem of the reality of matter, and concludes by subverting every argument in its favour, except what he takes to be the assertion of Scripture. Berkeley, who did not see this in the same light, had scarcely a step to take in his own famous theory, which we may consider as having been anticipated by Malebranche, with the important exception that what was only scepticism and denial of certainty in the one, became a positive and dogmatic affirmation in the other.
[793] L. i., c. 10.
43. In all our sensations there are four things distinct in themselves, but which, examined as they arise simultaneously, we are apt to confound; these are the action of the object, the effect upon the organ of sense, the mere sensation, and the judgment we form as to its cause. We fall into errors as to all these, confounding the sensation with the action of bodies, as when we say there is heat in the fire, or colour in the rose, or confounding the motion of the nerves with sensation, as when we refer heat to the hand; but most of all, in drawing mistaken inferences as to the nature of objects from our sensations.[794] It may be here remarked that what Malebranche has properly called the judgment of the mind as to the cause of its sensations, is precisely what Reid denominates perception; a term less clear, and which seems to have led some of his school into important errors. The language of the Scottish philosopher appears to imply that he considered perception as a distinct and original faculty of the mind, rather than what it is, a complex operation of the judgment and memory, applying knowledge already acquired by experience. Neither he, nor his disciple Stewart, though aware of the mistakes that have arisen in this province of metaphysics by selecting our instances from the phenomena of vision instead of the other senses, have avoided the same source of error. The sense of sight has the prerogative of enabling us to pronounce instantly on the external cause of our sensation; and this perception is so intimately blended with the sensation itself, that it has not to our minds, whatever may be the case with young children, the least appearance of a judgment. But we need only make our experiment upon sound or smell, and we shall at once acknowledge that there is no sort of necessary connection between the sensation and our knowledge of its corresponding external object. We hear sounds continually, which we are incapable of referring to any particular body; nor does anyone, I suppose, deny that it is by experience alone we learn to pronounce, with more or less of certainty according to its degree, on the causes from which these sensations proceed.
[794] C. 12.
44. Sensation he defines to be “a modification of the soul in relation to something which passes in the body to which she is united.” These sensations we know by experience; it is idle to go about defining or explaining them; this cannot be done by words. It is an error, according to Malebranche, to believe that all men have like sensations from the same objects. In this he goes farther than Pascal, who thinks it probable that they have, while Malebranche holds it indubitable, from the organs of men being constructed differently, that they do not receive similar impressions; instancing music, some smells and flavours, and many other things of the same kind. But it is obvious to reply that he has argued from the exception to the rule; the great majority of mankind agreeing as to musical sounds (which is the strongest case that can be put against his paradox), and most other sensations. That the sensations of different men, subject to such exceptions, if not strictly alike, are, so to say, in a constant ratio, seems as indisputable as any conclusion we can draw from their testimony.
45. The second book of Malebranche’s treatise relates to the imagination, and the errors connected with it. “The imagination consists in the power of the mind to form images of objects by producing a change in the fibres of that part of the brain, which may be called principal because it corresponds with all parts of the body, and is the place where the soul, if we may so speak, immediately resides.” This he supposes to be where all the filaments of the brain terminate; so difficult was it, especially in that age, for a philosopher, who had the clearest perception of the soul’s immateriality, to free himself from the analogies of extended presence and material impulse. The imagination, he says, comprehends two things; the action of the will and the obedience of the animal spirits which trace images on the brain. The power of conception depends partly upon the strength of those animal spirits, partly on the qualities of the brain itself. For just as the size, the depth, and the clearness of the lines in an engraving depend on the force with which the graver acts, and on the obedience which the copper yields to it, so the depth and clearness of the traces of the imagination depend on the force of the animal spirits, and on the constitution of the fibres of the brain; and it is the difference of these which occasions almost the whole of that vast difference we find in the capacities of men.
46. This arbitrary, though rather specious hypothesis, which, in the present more advanced state of physiology, a philosopher might not in all points reject, but would certainly not assume, is spread out by Malebranche over a large part of his work, and especially the second book. The delicacy of the fibres of the brain, he supposes, is one of the chief causes of our not giving sufficient application to difficult subjects. Women possess this delicacy, and hence have more intelligence than men as to all sensible objects; but whatever is abstract is to them incomprehensible. The fibres are soft in children, and become stronger with age, the greatest perfection of the understanding being between thirty and fifty; but with prejudiced men, and especially when they are advanced in life, the hardness of the cerebral fibre confirms them in error. For we can understand nothing without attention, nor attend to it without having a strong image in the brain, nor can that image be formed without a suppleness and susceptibility of motion in the brain itself. It is, therefore, highly useful to get the habit of thinking on all subjects, and thus to give the brain a facility of motion analogous to that of the fingers in playing on a musical instrument. And this habit is best acquired by seeking truth in difficult things while we are young, because it is then that the fibres are most easily bent in all directions.[795]
[795] L. ii., c. 1.