a physical efflux of species, and taught instead, that objects effected modifications in the mind by acting on the sense-organs through motions in the intervening media. The term species was later on employed to denote these modifications by which the mind is made to apprehend the exterior object. In this sense, which is that accepted by the greatest philosophers of the middle ages, such as St. Thomas, Albertus Magnus, and Scotus, the species is not an entity which has immigrated into the mind from the object, but a modification or disposition awakened in the mind by the action of the object. It is, in fact, the apprehensive act by which the mind responds to the stimulus.

The adjective intentionalis was attached to the term species to signify that the apprehensive act, though truly reflecting the external object, does not resemble it in nature. The mental modification was held to be merely a psychical or spiritual expression of the material thing. Resemblance is of many kinds. A photograph, or a statue, is, in a certain sense, utterly unlike a man formed of flesh and blood; the blind man's representation of a circle by the sense of touch, is very different from the visual image of the same figure; the intellectual ideas aroused by the words, "equality," "colour," "square," must be widely divergent from both the image and the reality to which they correspond. Yet, in spite of these unlikenesses, there exist genuine relations of similarity between such pairs of things as those just mentioned. The scholastic writers adopting this view, taught that our know

ledge, although in itself, as a mental activity, opposed in nature to material reality, does, nevertheless, truly mirror the surrounding world. They held that though neither the tactual nor the visual image resembles in nature the brass circular substance presented to the sense, yet both accurately reflect and are truly like the external reality; and they called these mental expressions of the object species intentionales.

Furthermore, as they held the mind to be capable of two essentially distinct kinds of cognition, sensuous and intellectual, they termed the apprehensive acts of the former species sensibiles, of the latter species intelligibiles vel intellectuales. In the genesis of the species they distinguished two moments or stages. The modification of the sensuous faculty, viewed as an impression wrought in the mind by the action of the object, was named the species impressa. The reaction of the mind as an act of cognitive consciousness was styled the species expressa. The latter term designated the sensation considered as a completed and perfect act of consciousness elicited by the soul; the former indicated the earlier stage of the process, the alteration in the condition of the mind looked at as an effect of the action of the object. The species proper, however, whether impressa or expressa, was an affection of the mind. The term species corporalis was sometimes used to signify the physical impression or movement pro

6 The existence of the species impressa is proved by the fact of memory. That the alteration or modification wrought in the soul by the act of perception must persist in some form, is established by the facility of representation and recognition.

duced by the object in the organism, but the strict meaning of the word species, and the only meaning of the term species intentionalis, was the mental state. Thus, neither the image of the object depicted on the retina of the eye, nor the nervous disturbance propagated thence to the brain, but the conscious act finally awakened, was held to be the true species or species intentionalis.

Rejecting the interpretation of the species as roving images, together with every theory which conceives them as representations mediating between the object and the cognitive faculty, the thought embodied in the doctrine is thoroughly sound. Unless we are prepared to maintain that our soul is born with all its future knowledge ready made, and wrapped up in innate ideas, we must allow that the physical world does somehow or other act on our faculties, and that our perceptions are due to the influence of material objects upon us. The mind does not determine all its own modifications, and the strongest volition is unable to make the deaf man hear a word, or the blind man see a colour.

7 The complete ignorance of modern philosophical writers regarding the teaching of the scholastic thinkers may be imagined, when even Hamilton confuses the maintenance of species with the doctrine of mediate perception, and so looks on St. Thomas and the great body of the schoolmen as hypothetical realists. (Cf. On Reid, Note M. pp. 852-857.) The familiar distinction of principia quibus, and principia ex quibus, rightly comprehended, would have saved him here. The species are not intermediate representations from which the mind infers the object, but psychical modifications by which the mind itself is likened, or conformed, to the object and thus determined to immediately cognize it. For an effective refutation of the charge of representationism against St. Thomas and the leading scholastics, based on the doctrine of species, cf. Sanseverino, Dynamilogia, pp. 390-400.

But this is to admit that the faculty is stirred into conscious life and informed by dispositions wrought in it by the perceived object. Further, unless we are ready to adopt the position of absolute scepticism, we must hold that knowledge does somehow correspond to reality. There is not a merely arbitrary connexion between the object and its apprehension. The latter is a true, though psychical expression of the former. This subject will be more fully dealt with hereafter, but we have said enough to justify the doctrine of species intentionales, as understood by St. Thomas, and the leading philosophers of the school. The modern writer may prefer to describe the perception of a triangle as a modification of the mind mirroring or reflecting in terms of consciousness the external object, but this is only in other phraseology the old doctrine.

PSYCHOPHYSICS.-By observing and comparing sensations varying in intensity, Weber, and later on, Fechner, discovered that the quantity of increment necessary to be added to a given stimulus in order to produce a sensation consciously distinguishable from that of the original stimulus, varies according to the force of that original stimulus. Thus, a weight of one ounce added to that of three, the light thrown upon a screen by one candle, in addition to ten, the addition of a single voice to a musical trio, all produce consciously increased sensations, yet, if we added but a single unit to a weight of ten ounces, to a light of five hundred candles, or to a chorus of twenty voices, the new sensation cannot be distinguished from the old. An elaborate series of experiments led to the conclusion that the increment required to be added to a given excitant in order to produce a sensation discriminable from the former mental state bears a constant ratio to the original stimulus, though this ratio differs in the several

senses. This generalization has been called Weber's or Fechner's Law. It has been otherwise formulated thus, To increase the intensity of a sensation in arithmetical progression, the stimulus must be increased in geometrical progression, or, the sensation increases as the logarithm of the stimulus. Thus, if a pressure of four ounces can be barely discriminated from that of three, the sensation caused by twelve ounces will be similarly just distinguishable from that of nine. It was further found that the stimulus must reach a certain minimum degree of force in order that any sensation can be felt. This minimum force measures the absolute sensibility of the organ, or part of the organ in question.

The chief statistical results which the advocates of Psychophysics claim to have established are the following. The absolute sensibility of the skin to tactual pressure varies in different parts from 002 to '015 of a gramme; the absolute sensibility of the skin to changes of temperaure varies from 2° to 9° Centigrade, the skin being about 30° Cent., that of hearing is the sound of a ball of cork, I milligramme weight, falling on a vibrating plate from a height of 1 millimetre, at a distance of 91 mm. from the ear; that of sight, the of the light reflected by white paper under the full moon. The ratio of the minimum increment to the original stimulus requisite to effect a new sensation is said to be, for tactual pressure, for sight, and for muscular strain. There is, moreover, a certain maximum, just as well as a minimum, beyond which the law admittedly does not hold. This maximum measures the height of the sensibility of the sense, and the interval between the height and the threshold constitutes the range of the sensibility of the sense.

The professed object of this line of investigation is to introduce quantitative measurement into Phenomenal Psychology, and so to reduce this branch of mental philosophy to the condition of an exact science. Now, whilst we readily admit that great care and ingenuity has been exhibited in carrying out these experiments, and that many of the facts established are curious and interesting, we believe that the advocates of Psycho