ii2. Two REALIST THEORIES OF SENSE PERCEPTION.

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Having justified the conviction that a real, external, extended

universe exists, we have next to inquire what degrees or orders

of knowledge as to its qualities and nature can be seen by reflec

tion to lie within the scope of our cognitive faculties ; or, in

other words, what information can the proper and common

sensibles convey to us about its qualities and nature. We can

best approach this question by considering how a reality such as

the external universe, now proved to be distinct from and other

than the individual knower, can come at all within the scope of

the latter s awareness. 1

Here scholastic psychologists are up to a certain point

unanimous. All alike teach that the process of sense perception

must be conditioned by the cognitive union of the external reality

with the individual perceiver, 2 and that this union is effected by

the action of the former on the latter. The perceiver is not always

in the act of perceiving. To pass from the condition of mere

capability to perceive, into the condition of actually perceiving

this, that, or the other datum or object, he must be determined by

the active influence of the external reality upon him. This in

fluence by way of efficient activity takes the forms of various

material energies (light, heat, sound, mechanical motion or im

pulse, etc.) in the universe external to the sentient self or Ego,

1 The scholastic theory of cognition, whether sensuous or intellectual, of external

reality through the medium of species intentionales, is obviously not intended as an

attempt to prove that we can know an external reality ; but, presupposing as already

established the truth that we do know such reality, it is an attempt to show how we

come to know it.

2 " Cognitum est in cognoscente " ; " perceptum est in percipiente " ; " sensibile

in actu et sensus in actu unum sunt " ; " animacognoscendo quodammodo fit omnia ".

But this immanence of the known in the knower, this identity of the known with the

knower, is not necessarily real ; it is only "cognitive," " intentionalis," " in ordine

cogniti:>nis," not "in ordine reali". Cf. no, 129.

PERCEPTION OF SENSE QUALITIES 65

and the form of nerve energy in the sense organs, nervous system,

and brain. These organs being animated by the mind or con

scious principle, the nerve impulse produces in the mind a cog- .

nitional determinant which the scholastics called the species

sensibilis impressa ". To this the conscious subject reacts by a

process whereby it becomes aware of something. This conscious

reaction or process or condition of actual awareness is what the

scholastics called the species sensibilis expressa. By describing

this process of conscious awareness, whether in its initiation

("species impressa"} or in its full actuality ("species expressa"\

as a "swedes" ("forma," eZSo?), the scholastics simply meant to

convey that by means of the cognitive process the conscious sub

ject or mind is conformed or assimilated to the apprehended or

known reality. And by describing the species as " intentionalis "

they meant to guard against the crude conception of cognition as

taking place by anything like a physical reproduction of the ob

ject in the subject, or a physical, material, photographic image of

the former in the latter. If they called the process of perception,

or the mind as perceiving, a likeness (^similitude"} or image

(" imago") of the perceived external reality, they added that this

likeness or image was sni generis, a something which mirrored,

in terms of vital, cognitive consciousness, the external reality.

In this theory, on which there is no need to enlarge in the

present context, 1 we must now fix our attention on one main

question. Is the whole mental modification or " impression " or

"determination," whereby the sentient subject is aroused into

the condition of awareness, or the whole subjective, psychic

process, including the psychic state or condition which is the

product or term of this process, the object which the conscious

perceiver becomes directly and immediately aware of? Or, to put

it in the technical language of scholasticism : Is the species

sensibilis expressa "id quod percipitur " ? Is it the mental

impression or state or condition itself that is the direct and

immediate object of the mind s awareness ? The result of the

perceptive process is conceived to be the production, in the per

ceiver, of a state of conformity or assimilation of the latter with

the external reality. Does this mean that there is constructed

or produced in the perceiver a mental -image or representation

of the extramental reality, and that it is this mental image or

1 For the psychology of the process, see MAHER, op. cif., pp. 51-4. C/. also

vol. i., 75, 76.

VOL. II. 5

66 THEORY OF KNOWLEDGE

representation which is immediately present in consciousness to

the perceiver, so that it is of this mental image as object that the

perceiver is directly and immediately aware? If these questions

be answered in the affirmative, then it will be further pointed

out that, this mental object of awareness being specifically

determined by the influence of the external reality, and being

the natural "cognitive" or " intentional " representation of the

reality, the perceiver by becoming directly and immediately

aware of the former, perceives, i.e. apprehends through it (" per-

capere"}, and in it and/;w it, the external reality. 1 The species

sensibilis expressa would thus be not only as a psychic, per

ceptive process, a means by which - the perceiver apprehends the

external reality, but also a direct object of awareness, 3 and at

the same time a medium in which 1 he perceives the external

reality mirrored or represented, and a sort of mental datum from

which, 5 by a process analogous to inference, he would attain to

conscious sense knowledge of the external reality.

The view just suggested expresses the theory of mediate or

representative sense perception. But there is the alternative

theory of immediate or intuitional or presentative perception,

referred to above (107). According to this view the species

sensibilis expressa, the whole mental modification and process,

with its resulting state or condition, is only the means by which 6

the external thing is directly presented to and consciously appre

hended by the perceiver : the process is not constructive of a

mental object which would be itself first apprehended, and in

and through which, as an image or representation, the represented

external reality would be mediately apprehended. The mental

or psychic effect of the action of the external reality on the

mind, and of the mental reaction thereto, on the one hand does

not itself come into consciousness or become an object of direct

awareness ; nor on the other hand does it wholly pass away with

the cessation of the conscious, perceptive act. The fact that the

mind can remember can recall, in their absence, and recognize

"external" data previously perceived, proves that the psychic

1 C/. vol. i., 75, p. 265, n. 3 ; infra, chap. xix.

2 " Medium quo." :< " Objectum quod percipitur."

4 " Medium in quo " or "per quod ". 5 " Medium ex quo."

fi " Medium quo." Perception is of course mediate in the sense that it is medi

ated or brought about by a mental process ; but in the view of perceptionists it is

immediate in the sense that no apprehended mental object intervenes between the

perceiver and the presented extramental reality.

PERCEPTION OF SENSE QUALITIES 67

effect of perception must have persisted, though unconsciously,

in the sentient subject. Now in the act of remembering, and

also in the act of imagining, what the mind directly contem

plates, what is immediately present to it, is not the external

reality, but a mental substitute of the latter, a mental image or

phantasma constructed by the mind in virtue of some permanent

or persisting dispositions wrought in it by its previous act or acts

of sense perception. But in the bare act of perception itself,

apart from mental imagery that may accompany it, it is the

external reality itself (i.e. some phase or aspect of it) that is,

according to the perceptionist theory, immediately present to,

and apprehended by, the perceiver.

Between those two views scholastics are divided. 1 Few have

defended the theory that the perceptive functions of all the ex

ternal senses are intuitive or immediate, that the immediate data

of all five senses are, as perceived, extramentally real. Those

who do defend perceptionism for the most part contend merely

that the immediate data of touch (resistance or impenetrability,

surface extensity), many add those of sight (coloured surface),

and some those of hearing (sounds), are as such extramentally

real. 2

The medieval scholastics generally regarded external sense

perception as a process directly intuitive of reality external to and

other than the perceiver? Nor does the fact that they spoke of

the species as a likeness (similitudo) or image (imago] or repre

sentation (representatio) of the reality militate against this inter

pretation, for they are emphatic in asserting that the species is

not that which is perceived (objectum quod percipitur), but only

remarks that outside Scholasticism the perceptionist theory has

practically no support : " Praeter Scholasticos vero, fere nemo Perceptionismum

tenet " (op. cit., p. 224). And he adopts the statement of VALENSIN (Dictionnaire

de th eol. cath., Art. Criticisme Kantien, col. 750) that the non-scholastic philosopher

who rejects perceptionism is not eo ipso a subjectivist but merely contends that there

is an epistemological problem in sense perception (I.e., n. i).

z lbid., pp. 224, 426.

3 St. Thomas, following Aristotle, teaches (hat the seusibilia propria, when not

being actually perceived, are still really in the things which constitute the external I

material universe, not however actually, but only potentially, as real potencies of

the latter to reveal itself to us as it actually does in our specifically different external

perceptions. This, however, as we hope to show, is. consistent with perceptionism.

JEANNIERE thinks that it is open to doubt whether St. Thomas was really a pro-

pounder of the theory of immediate sense perception, and quotes (op. cit., pp. 409-

10) a passage from the De Veritate (i., n ; cf. i., 17, 2 ad i ; Hi., 75, 5 ; 76, 8)

which seems to imply the theory of mediate or representative perception.

68 THEOR Y OF KNO WLEDGE

the means by which (medium quo] the external reality is perceived :

but conceiving all knowledge as an assimilation or conformity of

the knowing subject with the known object, and so, as a sort of

reproduction of the latter in the former, they regarded the species,

i.e. the determination of the cognitive process by the external

reality, as the principle whereby this mental assimilation or con

formity is effected.

It is a mistake, therefore, to represent scholastics generally as teaching

that in sense perception there is question of two sets of sense qualities, a

set of extramental external qualities in the things, and a set of internal

qualities in the consciousness of the perceiver. 1 In distinguishing (with

Aristotle) between the " potential " condition of sense qualities when unper-

ceived, and their "actual" condition when being perceived," the medieval

scholastics had not at all in contemplation the modern distinction between

"states of consciousness" and their "extramental correlates," or the conse

quent problem of the similarity of the latter to the former and the inferribility

of the latter from the former. It is this modern distinction which Jeanniere, 3

for instance, presupposes when he inquires " whether or not it is certain that

there exist formally in things qualities corresponding to the sense qualities

regarded subjectively, whether, e.g., colours exist in things " ; and when

he replies, " Such existence must be admitted if it can be shown that the

[conscious] impression of colours cannot be explained unless colours exist, as

such, in things, or that colours cannot exist causally in things unless they exist

formally also in things". Then he goes on to contrast the "common

scholastic view " (especially of the medieval scholastics) with the view of

"most modern philosophers " (including many scholastics whom he cites 4 ),

in the following terms : " The scholastics commonly considered the sense

qualities in us to be altogether similar to the qualities which exist outside us

in bodies. Nowadays, however, most philosophers teach that sense qualities

consist causally [i.e. as outside us in bodies ] not in any quality of things

but in a quantitative element, i.e. in certain vibratory motions of the air or

the aether. Such motions undoubtedly exist ; but who will prove that they

exist without any qualitative elements ?" " The modern " representationist "

attitude is here properly indicated ; and we shall duly examine its tendency

to regard the extramental material universe as a system of merely quantita

tive, i.e. space-filling and moving realities. But the first sentence, in which

the author describes the common view of scholastics, scarcely does justice to

these philosophers, and for the reason already stated, viz. that they did not

contemplate huo sets of known or knowable qualities at all, but rather one set

of extramental qualities and another set of mental or cognitive processes or

perceptions, of which these extramental qualities were the directly appre

hended terms or objects. 6

1 Cf. infra, 129. a Infra. 1*1-3. " O/. df., p. ^6.

4 Cf. infra, p. 69, n. T. s Op. cit., ibid, (italics ours).

C/. */ra, 121, 125.

PERCEPTION OF SENSE QUALITIES 69

Modern scholastics lean perhaps rather to the side of mediate

or representative sense perception. 1 This is mainly owing to the

difficulties which modern scientific discoveries in the domains of

physics and physiology are supposed to have raised against the

view that the " sense qualities " of which we are directly and im

mediately aware in conscious sense perception are in the external

reality independently of our perception of the latter. No doubt

the physical sciences have taught us much that was unknown in

the Middle Ages regarding the energies of matter and the laws

and modes of their operation ; the physiology of the sense

organs, the brain and the nervous system, has shed much new

light on the physiological basis of sense consciousness ; and ex

perimental or physiological psychology has investigated very

closely the connexion between the conscious phenomena of sense

perception and their organic conditions and correlates in the

brain and the nervous system. But whether the information

brought to light by such researches can help us in any way to

determine whether or how far the data or objects of which the

conscious perceiving subject becomes directly and immediately

aware in sense perception are in the external material universe

in the absence of all perception of them ; or are " extramental "

indeed, but dependent on the perceivers organism for what they

are, when he is actually perceiving them ; or are purely mental

or conscious effects of external, material energies, this is a

larger question on which these sciences have not thrown much

light, 2 and which will be decided gradually in the sections to

follow.