CHAPTER EIGHTEENTH.

CASUAL CONNECTIONS OF THOUGHT.

§. 205. Association sometimes misleads our judgments.

THERE HERE are some cases, where the power of association so misleads us, that we cannot easily form a correct judgment of the true nature of things. Every object of thought, in order to be fully understood, ought to be so much in our power, that we may examine it separately from all other objects. Whenever, therefore, it happens from any circumstances, that the power of association so combines one object of thought with another, that the object cannot readily be looked at and examined by itself, it so far has the effect to perplex and hinder correct judgment. It will be found, when we look into our minds. that there exist a few associations or combinations of thought of this kind, which are obstinate and almost invincible; and there are very many of a less degree of strength, but which have a considerable effect in disturbing the just exercise of the intellect, and require much care in their detection and eradication. The latter class will be examined at some length in the chapter on PREJU DICES; some prominent instances of the former class will be considered here, and, for the want of a better phraseology, we shall arrange them together under the head of CASUAL CONNECTIONS OF THOUGHT.

Of these a number of instances descrve a special attention. To explain the origin and to correct the erroneous tendencies of all such connections of thought, a

though the number of such as we have now in view cannot be large, would occupy us too long. The examination of a few somewhat striking instances will not only throw light on the philosophy of the mind in general, but will be of some practical benefit.

§. 206. Connection of our ideas of extension and time. EXTENSION is reckoned among the simple ideas, although it is derived from more than one sense; it is, therefore, difficult to define it so as to make it more clear, than it has already become by each one's experience. It perhaps approaches the nearest to a definition or rather description of it, to say, that it is the distance between the parts of the same object, where in the intermediate parts there is a continuity of the same substance.-We get the idea of TIME, which comes under the class of SIMPLE MODES, by considering any part of duration, as set or marked off by periodical measures, such as hours, days, or years. It is well known, whatever may be the cause of it, that people are generally in the habit of considering time, as a sort of modification of space or extension. This observation may not appear perfectly obvious at first. But the expressions, which we apply to intervals of duration, are an evidence of its truth.

We say before such a time or after such a time, the same as before or after any material object; we speak of a long or a short time with no more hesitation than of a long or short distance, of a long or short bridge, or railway, or any other object of extension. We utter ourselves precisely in the same way we should do, if we were certain of having detected some real analogy between the two, between length and shortness in material substances, and what are called length and shortness in time. But it is not too much to say, that there is no such analogy, no such similitude; nor is it worth while to anticipate, that we shall ever be able to detect such analogy or similitude, until we can apply the measures of feet, ells, roods, &c., to hours, and days, and weeks. How then can it be accounted for, that we apply terms nearly in the same way,

as if this were the case, and, as if such measurements could be made ?

The strong association of these ideas has most probably arisen in this manner, viz., from our constantly measuring one of these quantities by the other. It is the common method to measure time by motion, and motion is measured by extension. In an hour the hand of a clock moves over a certain space; in two hours over double the space, and so on. -No doubt it is convenient to apply the terms "long" and "short," "before" and "after," and others similar, to time. We could not well dispense with them. But it ought to be remembered, if we would have right notions of things, that the application of those expressions has arisen from the mode in which we measure time, and that time and space or that modification of space which we call extension are essentially distinct in their nature.

§. 207. Of high and low notes in music.

We speak of high and low in reference to notes in music, the same as of the high or low position of material bodies. There is supposed to be some analogy between the relation, which the notes in the scale of music bear to each other, and the relation of superiority and inferiority in the position of bodies of matter. But it is impossi ble to prove the existence of such analogy, however generally it may have been supposed; and the supposition itself of its existence has no doubt arisen from a casual association of ideas, or, in the expressions placed at the head of this chapter, in a casual connection of thought. A proof of this association of ideas being purely accidental is that an association, the very reverse of this, was once prevalent. It is remarked in the preface to Gregory's edition of Euclid's works, that the more ancient Greek writers considered the grave sounds as high, and the acute ones as low. The present mode of speaking on the subject is of more recent origin; but at what time and in what way it was introduced cannot be asserted with confidence. In the preface just referred to, it is, however

observed, that the ancient Greek custom of looking upon the grave sounds as high and the acute as low, precisely the reverse of what is now common, continued down until the time of Boethius. It has been conjectured with some ingenuity, that this connection or association of thought among the Greeks and Romans, for it was equally prevalent among both, might have been owing to the construction of their musical instruments. The string, which sounded the grave or what we call the low tone, it has been supposed, was placed highest, and that, which gave the shrill or acute, had the lowest place. If this conjecture could be ascertained to be well founded, it would strikingly show, from what very slight causes strong and permanent associations often arise. It is hardly necessary to observe, that it is important to examine the origin and progress of such associations, in order that we may correct those erroneous and illusive notions, which will be found to be built upon them.

§. 208. Connection of the ideas of extension and colour. There is no necessary connection between colour, as the term is commonly employed by philosophers, and extension. The word COLOUR properly denotes a sensation in the mind; the word EXTENSION, the quality of an external, material object. There is, therefore, no more natural connection and no more analogy between the two, than there is between pain and solidity. And yet it so happens that we never have the sensation or idea of colour without at the same time associating extension with it; we find them, however different they may be in their nature, inseparable in our thoughts. This strong association is formed in consequence of our always perceiving extension at the very time, in which the sensation of colour is excited in the mind. The perception of the one, and the sensation of the other have been so long simultaneous, that we have been gradually drawn into the belief, that, on the one hand, all colour has extension, and, on the other, all extension has colour. But what we call colour being merely a state of the mind, it is not possible, that it should

with propriety be predicated of any external material substances. Nor is it less evident, if colour be merely a sensation or state of the mind, that matter can exist, and does exist without it.

But what has been said will not satisfy all the queries, which may be started on this point, unless we remark also on the ambiguity in the word COLOUR. The view, which has been taken of the connection between colour and extension, is founded on the supposition, that colour denotes a sensation of the mind and that merely. It seems to be supposed by some writers, that the word colour has two meanings, and that it is thus generally understood;—(1) It denotes that disposition or arrangement in the particles of matter, which not only causes the rays of light to be reflected, but to be reflected in different ways;-(2) It denotes that mental sensation, which follows, when the rays have reached the retina of the eye. When people use the term with this diversity of signification they can say with truth, that external bodies have colour, and also that colour is a sensation of the mind. It may be said also in the first sense of the term, which has been mentioned, that colour has extension, because particles of matter have extension. But it is by no means evident, that people generally make this distinction, although some may. There is great reason to think, that they commonly mean by the term the appearance of colour or the sensation in the mind; and they no doubt do in general regard this appearance or sensation, as belonging to external objects, as being in some sense a part of those objects, and as having extension. How erroneous this supposition is, has already appeared!

§. 209. Whether there be heat in fire, &c.

The questions, Whether there be heat in fire, coldness in snow, sweetness in sugar, and the like, seem well suited to the inquisitive and nicely discriminating spirit of the Scholastic ages. Whether bodies have colour, a point of inquiry in the last section, is another question of essentially the same character. Although well suited to exercise the ingenuity of the Schools, they are far from being with