so far as it has any validity, we are said to reason by analogy.

Argument from Analogy. - Argument from analogy is defined by Jevons as "direct inductive inference from one fact to any similar fact." The same author gives the following example: "Thus the planet Mars possesses an atmosphere, with clouds and mist closely resembling our own; it has seas, distinguished from the land by a greenish color, and polar regions covered with snow. The red color of the planet seems to be due to the atmosphere, like the red color of our sunrises and sunsets. So much is similar in the surface of Mars and the surface of the earth, that we readily argue there must be inhabitants there as here. All that we can certainly say, however, is that if the cir cumstances be really similar, and similar germs of life have been created there as here,1 there must be inhabitants. The fact that many circumstances are similar, increases the probability. But between the earth and the sun, the analogy is of a much fainter character. We speak, indeed, of the sun's atmosphere being subject to storms and filled with clouds, but these clouds are heated probably beyond the temperature of our hottest furnaces; if they produce rain, it must resemble melted iron; and the sun-spots are perturbations of so tremendous a size and character that the earth, together with half a dozen of the other planets, could readily be swallowed up in one of them. It is plain, then, that there is little or no analogy between the sun and the earth, and we can, therefore, with difficulty form a conception of anything going on in a sun or a star."

1 Italics are mine.

QUESTIONS.

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Uncertainty of it. This kind of reasoning is more uncertain than inductive reasoning. Jevons speaks of the similarity between so many circumstances in the case of Mars and the earth as increasing the probability that the former is inhabited because the latter is, and at the same time says that "all we can certainly say is, that if the circumstances be really similar, and similar germs of life have been created there as here, there must be inhabitants." Need I say that in the very nature of the case we neither know nor can know anything about whether "similar germs of life have been created there as here," and that our knowledge of the extent to which circumstances are similar is so limited that any talk of probability is absolutely without foundation ? All that the facts warrant us in saying is, that for aught we know Mars may be inhabited, but he who claims to be able to say that it probably is, lays claim to a larger amount of knowledge than falls to the lot of mortals.

QUESTIONS ON THE TEXT.

I. What is the difference between induction and generalization? 2. Show that induction presupposes generalization.

3. State and illustrate the two assumptions that underlie nearly all our inductions.

4. What is the law of Parsimony?

5. Define and illustrate argument from analogy.

6. What seems to you its logical value?

SUGGESTIVE QUESTION.

Give illustrations from your own experience of over-hasty induc

tions.

We have studied sensation, perception, memory, imagination, conception, judgment, and reasoning - all modes of intellectual activity. If we pass them in rapid review before us, we shall see that in all of them the mind is discriminating or noting differences, and assimilating or noting resemblances.

Assimilation and Discrimination in Sensation.-What is it to know a sensation? It is to discriminate or mentally separate it from all other sensations. A child has many sensations which it does not know; many sensations which it confuses with other sensations. But a sensation confused with other sensations is a sensation put in the wrong class precisely as, if one were sorting out ribbons of different colors, the confusing of purple with blue would lead to the mixing of these two kinds of ribbons.

In Perception. So likewise in perception. The first act of the mind in perceiving is to separate mentally the thing perceived from everything else. You remember that, in the lessons on Attention, we saw that what we perceive depends upon what we attend to. The mind in attention simply singles out the thing attended to from

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everything else, and that is discrimination. A dog may stand before you, but if, through preoccupation or from any other cause, you do not discriminate it from the objects. about it, you do not know it. Discrimination, however, is

not all that is essential to knowledge. As a matter of fact, when we discriminate we usually know, because assimilation, or the act of putting a thing discriminated into a class, usually follows so closely upon the act of discrimination that the two seem to be identical. But they are not. To pick a piece of blue ribbon out of a scrap bag is one thing; to put it in a box with other blue ribbons is an entirely different thing. A child, seeing a dog, may discriminate it from all other objects, but until he perceives its resemblance to something else, until he assimilates it, he does not know it.

In Memory. So likewise with memory.

What is it to have a perfect recollection of any event? It is to have a definite knowledge both of the event and of the time when it happened. If the event is indistinct, it is not perfectly remembered, and its indistinctness is due to imperfect discrimination and assimilation. If we are in any doubt as to the time, it is because we do not perfectly discriminate it from other times, and do not perfectly assimilate it to other times. The event happened, say, at eleven o'clock yesterday, but I am uncertain whether it was eleven or twelve, or whether it happened yesterday or the day before-that is, I do not discriminate the hour. and the day when it happened from all others.

Possibly you think that in this latter case there is no assimilation. Inasmuch as in any one place there is but one point of time known as eleven o'clock, April 26, 1890,

the question may be asked as to how it is possible for assimilation of such a fact to take place. The question can be readily answered if we bear in mind that the state. of mind corresponding to the fact "eleven o'clock yesterday" is a complex concept. Before a child can know what is meant by "eleven o'clock yesterday," he must know the meaning of "yesterday" and "eleven o'clock,” and this is possible only by discrimination and assimilation. But with the concepts of these two facts as elements, all that is necessary to the formation of the complex concept expressed by the phrase "eleven o'clock yesterday" is a synthesis of the two through the exercise of the constructive imagination. The product of constructive imagination is, of course, an image; but as we can take the image of red color to illustrate the concept color, so we can take any image to illustrate the corresponding concept.

In Conception. We have seen that the three processes involved in conception are comparison — putting the attention on two or more objects at the same time, discriminating them from all other objects; abstraction-withdrawing the attention from their unlike qualities and fixing it upon their resemblances, assimilating them; and generalization - extending their name to all other objects having similar qualities a further act of assimilation.

In order to judge, we must know the subject and predi cate; and to do this, we must discriminate and assimilate them. I can not judge that oak trees lose their leaves in autumn unless I know what oak trees are, and what is meant by "losing their leaves in autumn." But to know oak trees, I must discriminate them from all other trees, and assimilate them to each other. The state of mind