a gas jet which you touch when you are looking for it, and one which touches you when you are not looking for it? Are you always receiving sensations when awake? Are you always expecting to receive other sensations?

Examine your definition of Sensation in the light of the foregoing examples and of the suggestions on page 53. Consider the following:

Some such analysis of Sensation as we have adopted on pages 62-64, will assist us in gaining an insight regarding the sequence of changes which must take place in the comparatively instantaneous and unconscious act of the reception of sense stimuli.

An attempt to frame an adequate formal definition of Sensation, however, is met with the following difficulties:

1st. There are countless external stimuli which come in contact with the end organs of the nerve, which are never noticed by us. It is agreed that a sensation must always be psychical, but (as has been pointed out) there are many occa sions in which we do not know what is the effect (if any) which the stimulus has upon conscious experience.

2nd. A sensation never exists by itself. It is only a part or element of the content of consciousness at any given time. It differs from other elements in that it is occasioned by the immediate action of stimulus upon the end organ of a nerve, and furnishes a basis for knowledge of external objects. It may, therefore, be said to be a presentative element of consciousness.

3rd. What we have in consciousness is not a series of isolated things, but a constantly changing process, and Sensation is therefore not a part of a static conscious content, but rather an aspect or phase of a reconstructive conscious pro

cess.

4th. Sensations are seldom, if ever, received in a haphazard way. While it is true that the stimulus must come in contact

with the end organ of the nerve it is equally true that the individual must receive and act upon the stimulus, otherwise there is no sensation. Certain sense stimuli are selected from others as worthy of attention. These stimuli may demand attention, as in the case of pain sensations, or they may be eagerly sought for, as in the case of the search for the gas jet in the foregoing example. The forms of response which the self-active individual makes to different received sensations, varies from the passing glance of sense-perception to vigorous and continued muscular and mental activity.

III.-FORMS OF RESPONSE TO SENSATIONS:

A.-Sense-perception.

Analysis. Consider the way in which the mind acts upon sensations in gaining a knowledge of the external object which furnishes the sense stimulus which occasions the sensation.

Have some object which you have not previously seen, (e.g., an orange), held up before your eyes near enough to be distinctly seen, but not close enough to admit of the exercise of any other sense upon it. Describe the color, form, size, distance, smell, taste and touch. What kind of sound would it make if it were to fall on the floor? Is it spherical? Have you seen the other side of it? How do you know it is spherical when you have not seen the other side? Would it be possible for a skilful artist to paint a flat surface so as to cause you to think you were looking at a real orange? With what other sense can you test whether the object you are looking at is spherical or flat? Could an artist paint the surface so as to deceive you in regard to the color, e.g., could he make a blue surface look yellow to you? Why do you think this orange is sweet, hard, etc.?

Make a list of the properties which you ascribe to the

orange, based on sensations which you are now receiving directly through the sense of sight, and another list of properties based on sensations which you think you would have experienced if you had used your other senses in examining the orange.

You find that the sensation of color came to you directly through the sense of sight; point out the way in which this sensation caused you to think that the orange was hard, smooth, spherical, etc. Would you have so interpreted this color sensation if you had never had any previous experience in looking at objects? Name other objects within your field of vision from which you are receiving color sensations at the same time that you are receiving color sensations from the orange. Can you look at an orange without seeing the color of surrounding objects? How and when did you separate the one from the other?

Do you have the idea of the orange as separate, that is, can you differentiate it from the other ideas and consider it by itself, analyzing it, etc.?

Which did you think of first, the color or the smoothness? How does the idea of the orange differ from the idea of virtue, or the idea of a centaur? Are you conscious that the object observed is not imagined or remembered, but is now located definitely in space?

Describe as fully as you can the action of the mind in the brief interval which elapsed between the time of the first reception of all the crude, undifferentiated color sensations coming from the entire field of vision on first opening your eyes, and the time when you perceived the orange as a definite known object in space.

We find that when we first open our eyes, a number of sensations beat upon consciousness, some from sight and some from other senses.

Of the sight sensations, some were from the orange and

some from other objects. The color sensations from the orange were quickly discriminated from all other sensations and, in the light of past experience, were made the basis for the interpretation of other sensations which we might have received had we used other senses in examining the orange. Finally, these were all united as qualities of one object, called an orange, located definitely in space and now seen and known by us.

Make a similar analysis of the way in which you gain a knowledge of other objects upon the basis of sensations, for example, when blindfolded, note the way in which by feeling an object, you can discover that it is an orange. Such action is called Perception (sometimes Sense-perception) and the result in consciousness is usually called a Perception or a Percept. It will be noted that perception is not limited to the sense of sight; we can perceive an object through any of the

senses.

Definition.-Write a definition of Perception.

Examine the following: "Perception is the act of interpreting sensations in such a way as to give us a knowledge of external objects."

"The consciousness of particular material things present to the sense is called Perception."

"Perception is the apperceptive or synthetic activity of mind whereby the data of sensation take on the forms of representation in space and time."

"Perceptions are mental contents due to the joint activity of sensation and apperception."

"The perceived thing is not simply the physically present vibrations of atoms and molecules which we call light or sound or what not. It is these vibrations as they are interpreted by the psycho-physical organism which exposes to them a nervous system already affected by past experiences that

enable it to get only certain specific kinds of results from the present syntheses."

"Perception is the gateway through which the mass of sensory excitations (save those grown purely habitual) must pass before they can be permitted to set up responses of the volitional kind."

Fig. 1

Interpretation of Sensations.-Describe what you see in Fig. 1. Is your perception of this object (that is, your knowledge of this line as a definite object in space from which you are receiving sensations of a black color) different from the sensations upon which the perception was based? In what ways have your past experience and education contributed to the formation of the percept? How long does the line seem to be? How far is it from your eye? Why is there less apperception in

volved

in this case

than there was in gaining the perception of the orange?

Examine Fig. 2. Describe what you see. Does the figure appear cubical? Are the lines all in one plane? Why does the line B F appear to be in a different plane from the line A B? If the figure be

H

G

cubical, how many degrees are there in the angle ABC? If at first sight Fig. 2 seemed to be the picture of the outline of a cube, how do you account for the fact that you considered the angles ABF and ABC each to be equal to 90