CHAPTER XI.

THE PERCEPTION OF BODY AS PRESENTING DYNAMICAL, STATICO-DYNAMICAL, AND STATICAL ATTRIBUTES.

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§ 317. The relation established between object and subject in the act of perception, is threefold. It assumes three distinct aspects, according as there is some kind of activity on the part of the object, on the part of the subject, or on the part of both. If, while the subject is passive, the object is working an effect upon it—as by radiating heat, giving off odour, or propagating sound; there results in the subject a perception of what is usually termed a secondary property of body, but what may be better termed a dynamical property. If the subject is directly acting upon the object by grasping, thrusting, pulling, or any other mechanical process, while the object is reacting, as it must, to an equivalent extent; the subject perceives those variously

The divisions thus designated, answer to those which Sir William Hamilton classes as Secondary, Secundo-primary, and Primary. While coinciding in the general distinctions drawn in his dissertation, I do so on other grounds than those assigned; and adopt another nomenclature for several reasons. One is that the names Primary, Secundo-primary, and Secondary, implying, as they in some degree do, a serial genesis in time, do not, as it seems to me, correspond with the true order of that genesis, subjectively considered; while, objectively considered, we cannot assign priority to any. Another is that these terms, as used by Sir William Hamil. ton, have direct reference to the Kantian doctrine of Space and Time, from which I dissent. And a third is that the terms above proposed are descriptive of the real distinctions among these three orders of attributes

modified kinds of resistance which have been classed as the secundo-primary properties, but which I prefer to class as statico-dynamical. And if the subject alone is active-if that which occupies consciousness is not any action or reaction of the object, but something discerned through its actions or reactions-as size, form, or position; then the property perceived is of the kind commonly known as primary, but here named statical.

The three classes of attributes thus briefly defined, which will hereafter be successively considered at length, are usually presented to consciousness together. The space-attributes are knowable only through the medium of resistance and the other force-attributes. Tangible properties are generally perceived in connexion with form, size, and position. And of the non-tangible ones, colour is mostly associated with the surfaces of solids, and cannot be conceived apart from extension of two dimensions. An object held in the hands and regarded by the eyes, presents to consciousness all three orders of attributes at once. It is known as something resisting, rough or smooth, elastic or unelastic; as something having both visible and tangible extension, form, and size; as something whose parts reflect certain amounts and qualities of light; and, on further examination, as something specifically scented and flavoured.

In conformity with the method hitherto pursued, of setting out with the most involved combinations, resolving these into simpler ones, and these again into still simpler ones; our analysis of the perception of body will be best initiated by taking an exhaustive perception as above described, and considering what are the relations among its various elements. And to simplify the problem, it will be well to treat first of those contingent attributes known as secondary, and here called dynamical; so that after having analyzed these in themselves, and in their relations to the necessary attributes, we may deal with the perception of necessary attributes as divested of everything that is extraneous,

§ 318. Beginning with these contingent attributes as contemplated in themselves, let us first consider the propriety of classing them as dynamical.

The most familiar ones are obviously manifestations of certain forms of force. Of sound, we know that it becomes sensible to us through vibrations of the membrana tympani, and that these vibrations are caused by waves in the air. We know, too, that the body whence these proceed must be thrown into a vibratory state by some mechanical force; that it thereupon propagates undulations through surrounding matter; and that in this purely dynamical action consists the production of sound.

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specting heat we know that it may be generated mechanically, as by compression or friction, and that, conversely, it is itself capable of generating mechanical force. We find that in its reflections and refractions, it conforms to the law of composition of forces; and that, by the now-established undulatory theory, its multiplied phenomena are resolved into dynamical ones. Further, there is the fact that on holding a thermometer near the fire, the same agent which causes in the hand a sensation of warmth causes motion in the mercury. The phenomena of colour, again, are reducible to the same category. The reflections and refractions of light are inexplicable, save mechanically; and only on the theory of undulations can polarization, diffraction, &c., be accounted for. Light is now recognized as one form of the primordial force, which may otherwise manifest itself as sensible motion, as electricity, as heat, as chemical affinity. In the fact that great heat is accompanied by luminosity, joined to the fact that great heat may be generated mechanically, we clearly trace the transformation; while, conversely, we find light producing a dynamic effect, alike in all photographic processes and in those molecular re-arrangements which it works in certain crystals. Nor must we forget that while, under ordinary circumstances, matter only reflects and modifies the light falling upon it;

The only

that of taste.

yet under fit chemical conditions, it becomes an independent source of light. Though not the immediate effects of radiant forces, odours are demonstrably dynamic in their origin. The established doctrine of evaporation implies that the giving-off of particles which produces odoriferousness, must be ascribed to molecular repulsion. Those diffused molecules constituting the scent of a body, must have been propelled from the surfaces of that body before. they acted upon the nostrils; and hence it follows that a certain form of activity in the object, is the efficient cause of a sensation of smell in the subject. secondary attribute not obviously dynamic is But the close alliance existing between taste and smell is almost of itself sufficient to prove that if one is dynamic so is the other. When we bear in mind that for a body to have any gustable property implies some degree of solubility in the saliva, without which its particles cannot be carried by endosmose through the mucous membrane of the tongue, and cannot therefore be tasted; and when we further bear in mind that the diffusion of particles through liquid is analogous to their diffusion through air, and that the molecular repulsion causing the last has its share in the first; we shall see further reason to consider the sensation of taste as due to an objective activity.

But the dynamic nature of the secondary attributes is most clearly seen when, instead of contemplating the object as acting, we contemplate the subject as acted upon. All can testify that the flavours of certain drugs are so persistent as to continue to give feelings of disgust, long after the drugs themselves have been swallowed. A pungent odour causes a sneeze; and the smell from a slaughterhouse or boneyard creates a nausea which so tyrannizes over consciousness, as to exclude every thought but that of escape. A flash of lightning, or any sudden change in the amount or quality of the light surrounding us, instantly changes the currents of our thoughts. And still more significant is the

fact that a strong glare abruptly thrown on his face, will often awaken a sleepy person. Similarly with changes of temperature. Any one standing with his hands behind him cannot have a red-hot iron put close to them without his ideas being at once directed into a new channel; and if the degree of heat passes a certain point, he will draw away his hands automatically. So, too, is it with sounds. They may create either pleasurable or painful states of consciousness. They often distract the attention against the will. When loud, they cause involuntary starts in those who are awake; and either waken those who sleep, or modify their dreams. If, then, in these extreme cases, the socalled secondary attributes of body are unquestionably dynamic, they must be so throughout. If we find the eyes made to water by mustard taken in excess; vomiting excited when squeamish by the smell of a steamer's cabin; a blinking of the eyes, and a painful sense of dazzling, caused by looking at the sun; a scream called forth by a scald or burn; an involuntary bound produced by an adjacent explosion; it becomes an unavoidable conclusion that those properties of things which we know as tastes, scents, colours, heats, sounds, are effects wrought on us by forces in the environment. The subject undergoes a change of state determined by some external agency, directly or indirectly proceeding from an object. Though there may arise in him, during the interpretation of its outward cause, various internally-determined states; yet, in so far as the change itself is concerned, he is simply recipient of an objective influence. In respect to all these so-called secondary attributes, the object is active and the subject is passive.

Let us next observe that, with the exception of taste which is in some respects transitional, these dynamical attributes are those by which objects act upon us through space. By means of the light it radiates or reflects, an outward thing renders itself visible when afar off. At