proof, nothing has yet been determined; but without some conception to direct investigation, there could be no proof for there would be nothing to prove. Sir Isaac Newton and Sir Humphrey Davy seem to me to have been richly endowed with the power of scientific combination. On the other hand, Dr. Priestly, though an eminent philosopher, seems to have possessed it in a very imperfect degree. Though his discoveries were numerous, and of the highest importance, yet all his theories of the changes which he observed have long since been exploded.

The power of philosophical combination, of necessity, improves with the progress of science. As the laws of nature and her modes of operation are better understood, we form conceptions more and more analogous to truth. We learn to think more and more in harmony with the ideas of the Creator; and, from a larger and more accurate acquaintance with the known, we are the better able to unravel the mysteries of the unknown. When it was observed that water would rise in a pump, the solution of the phenomenon at first said to be given was that nature abhorred a When it was found that it would not rise more than thirty-two feet, this fact was explained by the theory that nature did not abhor a vacuum more than thirty-two feet. Can it be that any of the hypotheses of the present day will seem as strange to our successors as this theory does to us?

vacuum.

With regard to the improvement of this faculty, a few words may be added at the close of this chapter. Let us refer to each of the three acts into which abstraction has been divided.

Analysis, or the power of distinguishing and separating from each other things which differ, may be employed either objectively or subjectively, as we are inquiring into

the qualities and relations of the world without us, or the energies and relations of the world within us.

So far as the accurate observation of the external world is concerned, much depends upon the delicacy of our senses, but probably no less upon the earnest attention with which we use them. A listless, careless observer never discovers anything. It is only by an intense direction of the mind to the objects of our inquiry, that we are able to detect changes and relations which have been hidden from preceding observers. Truth reveals herself not to those who pay her mere formal and perfunctory service, but to those who render to her the earnest and heartfelt homage of the whole soul.

Acuteness in the analysis of mental phenomena requires an equal earnestness, though it is differently directed. We here find it necessary to cultivate the habit of withdrawing from all external objects, and fixing our attention on the revelations of our own consciousness. Few men can do this without long-continued and patient effort. With such effort, however, most men can attain to it. We must learn to look calmly and steadily upon a mental phenomenon. If there appear in it the slightest indications of complexity; if, when examining it from different points of view, the least shade of difference be cognizable in our consciousness; or, if, on comparing two forms of thought, which seemed to us identical, there arises within us the intellectual feeling of dissimilarity, we must pause until we are thoroughly satisfied on the subjects of our inquiry. It is by listening to the first suggestion of a difference, that we learn to determine the character and relations of our mental phenomena.

If we would enlarge our power of generalization, I know of no better method than to study the generalizations of nature. Admirable lessons of this sort are found in the natural sciences,— chemistry, physiology, geology, etc. No

finer exercise for the power of generalization can be desired, than to take a single important chemical law, and trace out its operations on the vast and the minute throughout the kingdom of nature. Having become familiar with these wide-spreading classifications, we shall be the better able to pursue the generalizations of the subjective. We may then take an intellectual or moral law, and, having clearly marked out its nature and limitations, follow out its effects on the character of individual and social man. The light which will thus dawn on the mind will frequently astonish the student himself. Patient thought in this direction will furnish explanations of phenomena, and suggest rules of conduct, which would hardly reveal themselves to any other mode of investigation.

To improve the power of philosophical combination, we need, most of all, to study the actual combinations of nature. The more familiar we become with them, the clearer will be the light shed upon the unknown. Much may also be learned from the lives of those who have been so fortunate as to extend the limits of human knowledge. By observing the manner in which they have labored, we may hope to be able to follow their example. This subject will, however, come again under consideration, when, in a subsequent chapter, we treat of scientific imagination.

REFERENCES.

Abstraction-Locke, Book 2, chap. 11, sections 9, 6, 10, 11; chapter 12, section 1; Stewart, vol. i., chapter 4; Reid, Essay 5, chapters 2, 3, and 4.

Why most words general-Locke, Book 3, chap. 3, sections 1-10 Reid, Essay 5, chap. 1.

Simple words not definable - Locke, Book 3, chap. 4, sections 4-11. Nominalism and Realism. - Cousin, sect. 5, last part; Stewart, vol. i., chap. 2, sections 2 and 3

CHAPTER V.

MEMORY.

SECTION I. ASSOCIATION OF IDEAS, OR A TRAIN OF THOUGHT IN THE MIND.

THE next faculty which we shall consider is Memory. As, however, its nature cannot be unfolded without a knowledge of the laws which govern the succession of thought in the mind, we shall devote to this subject a preliminary section.

Every person is conscious of the fact that, during his waking hours, his mind is continually engaged in thinking. Were any one to ascertain that an hour, or even a few minutes, had elapsed, in which he had been conscious of no thought, he would know that, unless he had fallen asleep, he must have been affected with some disease which had for the time paralyzed his intellectual powers.

And yet more; we are all conscious that it is impossible, without severe and long-continued effort, to fix the mind continuously upon any particular thought. It naturally, and without effort, passes from one idea to another, and it requires a determination of the will to detain it upon any one subject. No interval seems to intervene between one thought and another. They succeed each other without any volition on our part, and frequently take a direction which we strive in vain to control. A train of thought will some

times seize upon the mind, and we are unable to disengage it. We strive to turn our attention to other objects, and, after repeated and strenuous efforts, succeed but imperfectly. And in general it may be remarked, that he has attained to uncommon intellectual self-discipline who is able to think at will, and for any considerable length of time, upon any subject that he chooses.

But, while all this is true, it is, on the other hand, true that our thoughts do not follow each other at random. There are what may be called laws of connection, by which their succession is governed. Whenever an unusual idea occurs to us, nothing is more common than to inquire for the reason of its appearance at that particular time and place. We take it for granted that it could not have occurred to us without being related to some other idea previously existing in the mind. We, therefore, refer back to the thoughts which were just before present to our consciousness, and endeavor to trace some connection between them and that for whose origin we are inquiring.

This fact may be abundantly illustrated by our own experience. The following examples will recall other instances to our recollection. Mr. Hobbes relates, in his Leviathan, that, upon some occasion, several gentlemen were engaged in a conversation respecting the civil war. One of them abruptly inquired the value of a Roman denarius. The question sounded oddly, and strangely at variance with the subject under discussion. Mr Hobbes relates that, on a little reflection, he was led to trace the train of thought which led to the inquiry. The subject of conversation, the civil war, naturally led the mind to the history of Charles I. The remembrance of the king suggested the treachery of those who delivered him up. The treachery in this case introduced the treachery of Judas Iscariot. The crime of Judas was at once associated with the price for which it was com