PERCEPTION.

 Reflection on the facts of sense experience, on our

spontaneous judgments regarding the immediate data of sense,

and particularly on the occasional illusions or deceptions or

erroneous interpretations of which we are the victims, convinces

us that we can rely on these spontaneous judgments only when

the whole conscious process takes place under normal conditions,

and that we can, by attending to the actual conditions, either

at the time or at least by reflection after the fact, either fore

stall or correct erroneous spontaneous interpretations. These

conditions are partly on the side of the perceiver and partly

on the side of the perceived datum or object.

The perceiver himself must be mentally and physically in

a sane and healthy condition. That is to say, he must be

awake and in such normal condition of mental and organic

health as to be capable of discriminating between a datum

which is a percept and a datum which is presented by imagination

through the abnormal functioning of the brain and nervous

system. 1 And secondly, in the case of a percept, the sense

1 Cf. JEANNIERE, op. cit., p. 419 : " postulatur . . . sanitas psychica subjecti, saltern

talis qua possit discernere sensationes proprie dictas a sensationibus imaginatis ".

9 6

organ or organs concerned in presenting it must be free from

any such disturbing and abnormal condition, whether congenital

or acquired, as would involve the presentation of this datum

otherwise than it would be presented by a sense organ or organs

in a normal condition. Hence a person affected by " colour

blindness " must correct his spontaneous interpretations of colour-

data so as to bring these judgments into conformity with those

of normal people. 1

Then, on the side of the external datum : the spatial and

physical conditions of the object under perception, and of the

medium between the object and the perceiver, must also be nor

mal in order to secure that the perceiver s spontaneous judgments

as to the qualities of the external datum or object be accurate.

Many, perhaps most, of those judgments are rather inferences

from what- we directly perceive, but inferences so natural, prompt,

and automatic that they are for the most part semi-conscious

or sub-conscious : a consequence of which is that unreflecting

people think they perceive, i.e. see, or hear, or touch what

they really only infer from that which is directly perceived. 2

In our perceptions of the " primary " or "common " sensible

qualities especially, the intellectual processes of judgment and

inference predominate. No doubt we perceive data endowed

with volume or three-dimensional extension, with shape or figure,

with spatial continuity and unity , or discontinuity and plurality,

with rest and motion. But the relative size of objects, their

relative positions in space, their distance from one another and

from the perceiver, their state of motion or rest relatively to

one another and to the perceiver, these are not percepts at

all, but estimates, i.e. interpretations and inferences, based on the

concrete percepts.

Now it is, of course, only experience that enables us to

determine in perception the physical, external conditions, which

1 The exact location of the data of the " organic sense " or " common sensibility,"

as it is called (cf. MAHER, op. cit., p. 69), i.e. organic processes and conditions,

aches and pains, etc., involves interpretation of these data, and is an endowment

gradually acquired by experience. It is in virtue of this acquired " sense habit "

that a person who has had a portion of a limb amputated continues to feel, i.e. to

locate spontaneously, pains, aches, etc., in the amputated portion of the limb.

3 Cf. Science of Logic, ii., 238, pp. 162-4. And, moreover, as we have already

remarked (118), apart from judgment and inference altogether, it requires close

introspective analysis to isolate the naked percept itself from the subjective

contribution made by the imagination and the faculty of association to the whole

conscious content in any individual process or act of external perception.

RELATIVITY OF SENSE QUALITIES TO PERCEIVER 97

are normal, and those that are abnormal : the conditions in which

we may as a rule rely on our spontaneous judgments of per

ception, and those in which such judgments will need correction.

It is, for instance, by experience we know the external conditions

in which a straight stick looks bent, in which an object at rest

appears to be moving or vice versa, in which two objects unequal

in size appear to be equal in size. It is by experience we know,

and allow for, the effects of coloured spectacles, of the stereoscope,

the microscope, the telescope, etc. By experience, too, we know

and allow for the effects of distance and perspective on the size

and shape of visible things.

 Reflection on the facts of sense experience, on our

spontaneous judgments regarding the immediate data of sense,

and particularly on the occasional illusions or deceptions or

erroneous interpretations of which we are the victims, convinces

us that we can rely on these spontaneous judgments only when

the whole conscious process takes place under normal conditions,

and that we can, by attending to the actual conditions, either

at the time or at least by reflection after the fact, either fore

stall or correct erroneous spontaneous interpretations. These

conditions are partly on the side of the perceiver and partly

on the side of the perceived datum or object.

The perceiver himself must be mentally and physically in

a sane and healthy condition. That is to say, he must be

awake and in such normal condition of mental and organic

health as to be capable of discriminating between a datum

which is a percept and a datum which is presented by imagination

through the abnormal functioning of the brain and nervous

system. 1 And secondly, in the case of a percept, the sense

1 Cf. JEANNIERE, op. cit., p. 419 : " postulatur . . . sanitas psychica subjecti, saltern

talis qua possit discernere sensationes proprie dictas a sensationibus imaginatis ".

9 6

organ or organs concerned in presenting it must be free from

any such disturbing and abnormal condition, whether congenital

or acquired, as would involve the presentation of this datum

otherwise than it would be presented by a sense organ or organs

in a normal condition. Hence a person affected by " colour

blindness " must correct his spontaneous interpretations of colour-

data so as to bring these judgments into conformity with those

of normal people. 1

Then, on the side of the external datum : the spatial and

physical conditions of the object under perception, and of the

medium between the object and the perceiver, must also be nor

mal in order to secure that the perceiver s spontaneous judgments

as to the qualities of the external datum or object be accurate.

Many, perhaps most, of those judgments are rather inferences

from what- we directly perceive, but inferences so natural, prompt,

and automatic that they are for the most part semi-conscious

or sub-conscious : a consequence of which is that unreflecting

people think they perceive, i.e. see, or hear, or touch what

they really only infer from that which is directly perceived. 2

In our perceptions of the " primary " or "common " sensible

qualities especially, the intellectual processes of judgment and

inference predominate. No doubt we perceive data endowed

with volume or three-dimensional extension, with shape or figure,

with spatial continuity and unity , or discontinuity and plurality,

with rest and motion. But the relative size of objects, their

relative positions in space, their distance from one another and

from the perceiver, their state of motion or rest relatively to

one another and to the perceiver, these are not percepts at

all, but estimates, i.e. interpretations and inferences, based on the

concrete percepts.

Now it is, of course, only experience that enables us to

determine in perception the physical, external conditions, which

1 The exact location of the data of the " organic sense " or " common sensibility,"

as it is called (cf. MAHER, op. cit., p. 69), i.e. organic processes and conditions,

aches and pains, etc., involves interpretation of these data, and is an endowment

gradually acquired by experience. It is in virtue of this acquired " sense habit "

that a person who has had a portion of a limb amputated continues to feel, i.e. to

locate spontaneously, pains, aches, etc., in the amputated portion of the limb.

3 Cf. Science of Logic, ii., 238, pp. 162-4. And, moreover, as we have already

remarked (118), apart from judgment and inference altogether, it requires close

introspective analysis to isolate the naked percept itself from the subjective

contribution made by the imagination and the faculty of association to the whole

conscious content in any individual process or act of external perception.

RELATIVITY OF SENSE QUALITIES TO PERCEIVER 97

are normal, and those that are abnormal : the conditions in which

we may as a rule rely on our spontaneous judgments of per

ception, and those in which such judgments will need correction.

It is, for instance, by experience we know the external conditions

in which a straight stick looks bent, in which an object at rest

appears to be moving or vice versa, in which two objects unequal

in size appear to be equal in size. It is by experience we know,

and allow for, the effects of coloured spectacles, of the stereoscope,

the microscope, the telescope, etc. By experience, too, we know

and allow for the effects of distance and perspective on the size

and shape of visible things.