EXAMPLES OF SENSATION.

169

referred to the countenance, and so on, just as I should have done had the sitter been there. When I looked at

the chair I saw the man. Gradually I began to lose the distinction between the imaginary figure and the real person, and sometimes disputed with sitters that they had been with me the day before. At last I was sure of it, I lost my senses, and

and then

all is confusion.

was thirty years in an asylum.'"1

These are a few of many cases that might be cited to show that sensations often exist when the nerve that leads to the brain is not stimulated. If we should hear a bell ring when the rope was not pulled, we should be sure that the same effect (swinging of the bell) existed as when the rope was pulled. So, likewise, when sensations exist in the manner described above, one can scarcely help believing that the bell was swinging without the rope being pulled that there was the change in the cortical centre that occasions and conditions sensation without the stimulation of the nerve that usually causes it.

These four physical antecedents, then the exciting cause, its action upon the nerve, change in the nerve, changes in the brain- usually precede the mental fact

that we call sensation.

Examples of Sensation.- If now you were asked to give examples of sensation, would you mention the hearing of a drum and the seeing of a rose? I do not believe you would. Let us run over the series of facts that result from the beating of a drum-vibrating air, action upon the auditory nerve, change all along the auditory nerve, change in the brain and see if we can not distinguish 1 Taine's Intelligence p. 46.

between the next term, the sensation, and the hearing of the drum. If you beat a drum in the presence of a newborn babe, will he hear it? No; he will have a sensation of sound, but he will not hear the drum. We may have sensations of sound, and not hear anything; sensations of color, and not see anything; sensations of smell, and not smell anything; sensations of touch, and not touch anything; sensations of taste, and not taste anything.

What do you mean when you say you see an apple? You mean, among other things, that you see a round object, good to eat, and with a pleasant odor when brought near the nose. Do you see its odor? No; you learn the odor of things through the sense of smell. Do you see its taste? Again, no; you learn the taste of things through the sense of taste. Do you see its roundness? No; you learn the shape of things by the sense of touch and the muscular sense. How, then, are you able to know by sight alone that an object before you has a certain shape, taste, odor, etc.?

To answer that question, suppose you ask yourself what a man would know of an apple who saw one for the first time, and who had never heard of one before. He would know its shape, but he would know nothing of its odor and taste. If he tastes and smells the apple, the next time he sees an object resembling it closely in appearance, it will be likely to occur to him that it resembles it in taste and smell also in other words, that it is an apple.

There is, you observe, a great difference between the experience of color which you have when you are looking at an apple, and the ideas of odor and taste that it suggests. The experience of color is a present sensation ;

DEFINITION OF SENSATION.

I7I

the ideas of odor and taste which it suggests are recollections of past sensations of taste and smell.

Definition of Sensation. We are now ready for the definition of sensation. A sensation is that simple mental fact that, under normal circumstances, directly follows the last change in the brain in consequence of the stimulation of a sensory nerve.

I say, I say, "directly shall not confuse

The color of an

Note carefully the italicized words. follows." If we bear that in mind, we the sensation with what it suggests. apple suggests its taste and odor; but until you actually taste and smell it, its taste and smell are not sensations, because they do not directly follow the last change in the brain resulting from the stimulation of a sensory nerve. The only thing that directly follows the last change in the brain is the sensation of color; the thought of the taste and smell of the apple are the result of the sensation, so that this change in the brain makes you think of its smell and taste through the sensation, or indirectly.

If we bear in mind the significance of the word "simple," it will save us from the same mistake. When you are seeing, hearing, touching, and tasting things, your experience is not simple. You have a sensation, and with it the recollection of sensations that it suggests.

Sensations of Sight and Seeing. We can now see how we can have a sensation of sight without seeing anything. If you are walking along a road, the various objects within the range of your vision probably produce sensations of sight. Will you see the objects in case they do? That depends on whether they suggest the recollection of past

sensations. But, as we know, what we recollect depends on what we attend to. When, therefore, you are absorbed in thought, the chances are that you will see very few of the objects that give you sensations of sight.

QUESTIONS ON THE TEXT.

1. Summarize the results reached in the last lesson.

2. What would be the logical course if one intended to write a comprehensive treatise on the subject of Psychology, and why?

3. Show that a large part of our knowledge takes its rise in sensations.

4. Give examples of sensations from each of the five senses, discriminating carefully their physical antecedents from the sensation. 5. Which of these physical antecedents may be dispensed with without preventing the sensation from existing, and why?

6. Define sensation. Distinguish it from what it suggests.

7. How can we have sensations of sight without seeing anything?

SUGGESTIVE QUESTIONS.

1. How would you explain the sensations experienced in dreaming? 2. If an explosion were to take place on a desert, in the absence of any mind, would there be any sound?

3. Is there any ambiguity in the words "sound," "coior," "taste,” "smell," etc.?

4. What is the real difference between physical and mental facts?

LESSON XIX.

SENSATION.

(Continued.)

1

Are Colors, etc., only Mental Facts? Let us imagine ourselves taking a walk on one of those perfect days in June that Lowell speaks of. The fresh, delicate green of the trees, the songs of birds, and the odors of a thousand flowers and blossoms, delight us. But in the midst of our enjoyment the subject of the last lesson occurs to us. We cease to enjoy; we begin to think. We ask each other if the conclusions reached in the last lesson, which seemed so true as we worked them out by gaslight, really do hold of the gorgeous panorama that lies spread out before us. Is the delicate green of the trees, the deep blue of the skies, merely a web of our own mental facts, a garment of our own making, with which, unconsciously to ourselves, we have covered up the unsightliness of nature? Are the so-called songs of birds merely echoes in our own souls of soundless motions without? In one word, are the colors and sounds and odors that seem to fill the scene before us only mental facts—things which, like the joys and sorrows, the hopes and fears, that make up our conscious life, exist in our own minds, and nowhere else?

Whatever reason may say, our first impulse is to answer with an emphatic negative. But as we follow in imagination the vibrations of air radiating from the birds in every