By the law of association, many ideas received directly from sensible objects, through the medium of different senses, become connected, and at last blended together, so as to form one very com plex, though apparently uncompounded, idea ; and this complex idea is often re called to the mind by a corresponding sensation, and, by association, becomes so connected wuth that sensation, that the complex idea itself is often mistaken for a part of the sensation. For instance, the sensation produced by the impression made by a globe on the sense of sight is, as can be proved, nothing more than that produced by a circle, with certain varia tions of light and shade; yet, immediately on the sensation being perceived, the ideas of its solidity, of its hardness, its magni tude, and of its being something external to one's self, (all of which have been de rived from the sense of touch, in connec tion with this object, or others in some re spect similar), immediately rise up in the mind in one blended form; by their com plete coalescence they appear to be one, and by their immediate and constant con nection with the sensation, they appear to the mind as a part of the sensation. Indeed, there are comparatively few people, who ever think that the sensation derived from the sight is nothing more than that derived from a minute picture delineated on the back part of the eye, called the retina. Things appear to us, at one glance of the sight, to be solid or flat, to be near or distant, to be large or small, to be conjoin ed with other things, or separate from them, to be parts of our own frame, or external to it, &c. and all this we appear to learn by the sight alone ; but the fact is, that all these ideas are derived from ano ther sense, at various times, and altoge. they blending together, and arising the moment the visible impression is commu nicated, they appear part of the visible impression. " The visible appearance of objects," as Berkeley observes," is a kind oflanguage, serving to inform us of their distance, magnitude and figure ;" no sooner are these signs presented to the mind, than with the rapidity of lightning the ideas associated with them succeed, and appear to have been communi oated by the sight, and to be in reality a part of the sensation.
The sensation thus connected with the complex idea is a perception. The ac curacy and vividness of the sensation de pend entirely upon the sensitive power and its organs : the accuracy and vivid ness of the perception depend partly upon the accuracy and vividness of the compo nent sensations, and partly upon the acti vity and energy of the retentive and asso ciative powers.
For a somewhat particular account of each sense, with statements respecting the share each has in forming our ideas, e. our notions and our feelings, we beg our readers to refer in this place to the following articles, in the order in which we here detail them; Sumv,Touca, Tms, Sims, and SOUND ; and presuming upon the perusal of those articles, we shall here make a few general observations respect ing sensations.
I. Sensations are the rudiments and elements of all our ideas ; that is, of all our thoughts and feelings. This is a position, which perhaps few of those who are unacquainted with the speculations of metaphysical writers would suppose to have been ever doubted. When an in fant enters into the world, there is no ap pearance of any ideas being in its mind ; and no one can doubt that if any human being could be deprived of all his organs and sensations, before any sensations had been received, that he would never have ideas. Yet it was once generally believ ed, that there are in ever human being ideas born with him, which were called innate. What they were, or in what re spects they differed from those which are indisputably received by means of the organs of sensation, was never, we ap prehend, pointed out. Indeed, the doc trine of innate ideas rests merely on an appeal to ignorance ; and as soon as any probable account of their origin is given, all support of it falls at once. Before the grand law of association was tolerably understood, the mode of the formation of many complex ideas could not be satis factorily ascertained ; and it must still be admitted, that we cannot in all cases fully trace the formation of our complex ideas ; but we can in a sufficient number to decide the point. Between those whose formation we can explain, and those whose we cannot, there is no fur ther difference, than our greater or less acquaintance with the individual steps of the process.
2. In the earliest exercise of the sen sitive power, sensations are simple, un compounded with the relics of former corresponding sensations ; but the sen sations very soon become perceptions, that is, they instantaneously recal the re lics of other corresponding sensations. This implies the exercise of the reten tive and associative power; but as per ceptions are almost uniformly produced by every exercise of the sensitive power, it may be proper to speak of them here in connection with sensations. That sen sations in a somewhat advanced state of mental culture are usually perceptions, any person may satisfy himself, by con sidering, that sensations are usually ac companied either with an idea of an ex ternal object causing them, or (if they are thereby the effect of the state of the bodily system) with an idea of the sen sation being in the part of the body in which the cause of the sensation exists; both of which are complex ideas, formed from a great number of impressions, and which could in no instance be produced by any exertion of the sensitive power. —We, therefore, in many cases, with out any impropriety, speak of percep tions and sensations Indiscriminately ; since a perception always implies a sen sation, and sensations most frequently are perceptions; and accordingly we shall find, in some writers, that they are con founded sometimes where they ought to be kept distinct.
3. Considering man as an intellectual being, the accuracy and extent of his perceptions are of the first moment. They are, in fact, the materials of all knowledge respecting external objects, and in the early stages of mental culture are the only objects of the understand ing. Now the accuracy and extent of the perception depends upon the vivid ness and efficaciousness of the compo nent sensations, and the number of them received from the same or similar objects in different situations, and through the medium of different senses. The object, therefore, of the early education of the human being should be, to invigorate the organs of sense. Independently of the effects of the general healthiness of the system, it appears decidedly probable, that the organs of sense are capable of being improved by exercise. It is the grand law of our frame, that moderate exertion increases the power of exertion ; and assuredly there are facts which lead to the same conclusion in this particular case. But this may be safely left to the natural effect of exertion. All that is to be done is, to afford children the oppor tunity of exercising their senses on a va Piety of objects, and as much as possible in a variety of situations. Some have supposed that the senses are not capable of improvement. We readily grant, that the superiority possessed by some over others, in the use of their senses, principally consists in the extent, and ac curacy, and vigour of their perceptions. Two persons, with equally good eyes, will see the same thing very differently, will have very different perceptions, though the se nsat ions can not as far aswe can judge, differ in any respect. Let two such per sons have a watch placed before each of them, as nearly as possible in the same situation in every respect ; suppose one minutely acquainted with the beautiful machine and the other unacquainted with it ; they have the same sensations, but how different their perceptions ; one sees a number of movements, of which he cannot discern the connection, nor point out the part it bears in the performance of the object ; the other at once perceives the mutual dependence of the parts, and the minutia of the whole structure, its excellencies and defects, &c. Our limits will not permit further illustration, but it is in the power of every one to trace it for themselves, by recollecting how differently the same thing appears to different persons of equally vigorous powers of sensation, and how differently it appears to the same person at different times. But all these things do not dis prove what we before stated respecting the improvement of the senses them. selves ; they merely point out, as another means to render sensation efficacious, that we should extend the perceptions, and render them accurate. This is, by giving extent and accuracy to the per ceptions, we render the sensations more efficacious, which we mentioned as one of the principal things upon which the extent and accuracy of the perceptions depend. To give vividness and effi cacy to the sensations, the organs of sense should then be exerted on various objects and in various situations ; a still more important mean is, to direct the at tention sufficiently to the objects of sen sation. in what manner it produces the effect we know not, but it is certain that the efficaciousness of sensations in pro ducing distinct ideas depends principally upon the degree of attention which those sensations receive. Hence, those who have the care of infants and children should give them every opportunity to keeptheir attention directed to the objects of their senses, and every means should be employed to lead them to such attention: a child intently gazing upon an object, or examining it with its little hands and lips, is as usefully employed in the cultivation of intellect as the fondest parent can wish. There is, however, more to be done in this connection, also, by allowing the child full scope for its own exertions, than by any direct efforts which can be made by others. When its attention is fixed, let it remain so ; if possible, let the objects of sense be brought under differ ent aspects, and exposed to the different senses. Before words become to a child the sign of voluntary action, all that can be done is, to expose it to sensations, and to allow them to fix the attention : but afterwards more direct efforts may be made, and the attention may be fixed by various other means than the mere action of the sensations themselves. Indepen dently of its value in providing materials for clear perceptions, it is of peculiar im portance to the future improvement of the understanding, and consequently to the moral culture, that the habit of fixed attention should be acquired; and we wish here to express our decided opinion, that the character of the intellect and affec tions, however much it may be modified by future cultivation, receives its stamp from the employment of the first few years of life ; that the education of the nursery is of almost incalculable moment in the mental and moral culture ; that by neglect of it, years of labour may be rendered requisite to compensate in some degree for it, and by a proper attention to it, a foundation is laid for a clear and vigorous understanding, and lively and pure affections. As far as the understand ing can be considered as separate from the affections, the primary object is, to gain clear and extensive perceptions, and fixed active attention; and respecting t hese the few observations which have been made may afford some useful hints to the thoughtful. Miss Hamilton has many ju dicious remarks on this subject, at the be ginning of the second volume of her work on education ; a work, which, though sometimes incorrect as to scientific ar rangement, and still more frequently as to precision of language, contains many highly valuable instructions for the cul ture of the human mind.