at the discovery of the laws of the data with which it deals, and at the organization of all its content into a single systematic whole. A completely organized system of knowledge would be one in which every part would imply every other, and he who understood the system perfectly could reconstruct the whole from any part. Cuvier claimed that a naturalist could reconstruct an animal from a single bone, and he himself, as noted by Huxley in the passage quoted above, gave evidence of the validity of his claim. Perfection of organization is not to be found in any natural science; the mathematical sciences show something approximating completeness, but they do not deal directly with concrete facts.

CHAPTER II

FIRST STAGES IN KNOWLEDGE

I. Facts and the Ways in Which They are Known.— Knowledge begins with the perception of facts; and these facts are of many kinds. What is a fact?

A fact is anything which exists; it is that which is real, apart from any opinion we may have about it or any attitude which we may take toward it; it is that which is as opposed to that which is merely imagined or conceived. When we ask for facts, we ask for something which shall be independent of any belief 1 or disbelief, approval or disapproval, on the part of any person. Some or all of these characteristics belong to laws, but fact is distinguished from law in being concrete and particular, instead of abstract and general.

A. PERCEPTION AND WHAT IT INCLUDES.-Facts are known primarily through perception and memory; they are known directly only by means of perception,

1 Belief and disbelief, whether true or false, are themselves facts; they are psychological facts. Belief in the Ptolemaic astronomy was a fact; that is, the belief actually existed. A false belief is one in which the thing believed is not a fact; it asserts or assents to something which does not really exist. Belief or disbelief may bring about changes in facts; in other words, give rise to new facts, as may any other existing thing. To say that a fact is independent of our attitude means that its existence and character are what they are apart from our attitude and aside from any possible effects which may be produced upon them by our attitude.

2 This position is confessedly dogmatic. Further reflection might show that nothing is independent, but for our present purpose this position is justified.

though there are various ways in which they may be known indirectly. One of the most important of these indirect means, and one which is an important element in all the rest, is inference; a perceived fact may be evidence to our minds of the existence of something which we cannot perceive,

Much that is often included under perception must be eliminated when we are trying to use the term with scientific accuracy. For example, we say that we perceive the inkstand upon the table, or a man on the other side of the street, or that lightning has set fire to a distant building, or that Mr. X is an able lawyer, or that history repeats itself, and so on. Are any of these pure perceptions? We may perceive certain events, but to "perceive" that history is therein repeating itself involves, at the very least, these inferences: that the words of historians represent what has occurred in the past; that they are competent and truthful and that we understand them; and that the events we perceive are really like those which they have described. In the example of the lawyer, we base our belief on observation of certain acts of his which have brought about desired results in spite of difficulties; and on the inferences that he understood the situation and intended to bring about the results which actually occurred. Again, though the flash and the distant light were perceived, the conclusions that the flash was lightning and that the light was that of a burning building in the distance, and that the first of these was the cause of the second, involve far more than perception. In such instances as these the presence of inference is evident and the importance of distinguishing

PERCEPTION AND INFERENCE

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what is perceived from what is inferred is obvious. The perception might be correct, while the inference was erroneous, or vice versa. By distinguishing the two, the problems of discovering error and of correcting it are much simplified.

But it is by no means easy to know where to draw the line between perception and inference. We should say ordinarily that we perceive the ink-well or the man across the street, but even in these cases there is something which is very like inference. A perception contains many different elements, and these get themselves before the mind in a variety of ways; comparatively little in any perception can be said to come directly from the object. In the perception of the ink-well or the man all that we get directly is a spot of color with certain variations of light, shade, and so on. But we seem to see an object in three dimensions, of a certain size, at a given distance from us, and possessing weight, resistance, a certain degree of hardness, a peculiar internal structure and an indefinite number of other qualities, which may be more or less definitely present to the mind. If we had not, in the past, found these qualities in combination with spots of color similar to those now present, we should not be aware of them now; but that does not mean that these qualities are simply remembered, for they are present to the mind as genuinely objective qualities, and we seem to be as directly aware of them as we are of the color, although reflection shows us that they could not be given by sight alone. They all seem to present themselves together, while in remembering a number of events, first one appears before the mind and then an

other; in perceiving an object, the qualities do not come forward one after another, but all seem to be present together in a single thing. A perception is a reaction of the mind to an object, quality, or event of some kind. A mind which has had little experience in a given field will react to an object in that field with a perception of a comparatively simple sort; if one had seen and handled oranges but had not tasted them, his perception would contain no suggestion of the flavor, as a blind man's perception contains no suggestion of color or other visual qualities.

Every time an object is perceived under new conditions something is added which will modify future perceptions in greater or less degree. The child builds up his perceptions gradually; from a first vague, indefinite perception he advances to one that is more coherent and complete.

The way in which any person will perceive an object will depend largely upon his past experience: different persons will consequently perceive the same object differently; as no two persons have ever had precisely the same experience, they will never see a given object in precisely the same way. But in most instances the differences will be slight, because there is so much that is common in the experience of all, and in the perception of ordinary objects the differences are usually small and comparatively unimportant.

"Fallacies" of Perception, and Their Causes.-We think of perception as a certain and infallible source of knowledge; but if in all perceptions there is a large addition from past experience it is clear that many of them are likely to be wrong. The present object may