we employ in our moral and metaphysical reasonings. "We may be assured of this," says Dr. Reid, "that the ambiguity of words, and the vague and improper application of them, have thrown more darkness on these subjects than the subtilty and intricacy of things. When we use common words, we ought to use them in the sense in which they are most commonly used by the best and purest writers in the language; and when we have occasion to enlarge or restrict the meaning of a common word, or to give it more precision than it has in common language, the reader ought to have warning of this, otherwise we shall impose upon ourselves and on him.”

While we are to affix a distinct and appropriate idea to every term we employ, we must beware of thinking that all the words in language admit of a logical definition. We may perfectly understand the meaning which we attach to certain terms when, in consequence of the simplicity of the objects they denote, it may be impossible to render that meaning more obvious otherwise than by the use of synonymous words. Definition, indeed, in every case, supposes that the acceptation of a word is explained by other words whose meaning is already known. We are only required, therefore, to define words that are uncommon, or that are used in an uncommon sense.

A little reflection will convince any one that the words of which we can give a proper and logical definition are not numerous. If, on the one hand, the things which they signify are perfectly elementary, or, on the other, expressive of the most enlarged and comprehensive ideas, they cannot, for reasons suffi

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ciently obvious, admit of explication. "No word," says the eminent philosopher to whom I have already alluded, can be logically defined, which does not denote a species, because such things only can have a specific difference; and a specific difference is essential to a logical definition. On this account there can be no logical definition of individual things, such as London or Paris. Individuals are distinguished, either by proper names, or by accidental circumstances of time and place, but they have no specific difference ; and, therefore, though they may be known by proper names, or may be described by circumstances or relations, they cannot be defined. It is no less evident, that the most general words cannot be logically defined, because there is not a more general term, of which they are a species. Nay, we cannot define every species of things, because it happens sometimes that we have not words to express the specific difference. Thus, a scarlet colour is, no doubt, a species of colour; but how shall we express the specific difference by which scarlet is distinguished from green or blue? The difference of them is immediately perceived by the eye, but we have not words to express it.

"There is no subject in which there is more frequent occasion to use words that cannot be logically defined than in treating of the powers and operations of the mind. The simplest operations of our minds must all be expressed by words of this kind. No man can explain by a logical definition what it is to think, to apprehend, to believe, to will, to desire. Every man who understands the language has some notion of the meaning of these words; and every man

who is capable of reflection, may, by attending to the operations of his own mind, which are signified by them, form a clear and distinct notion of them; but they cannot be logically defined*."

Of what importance it is to be familiar with these very obvious and elementary truths, the history of science sufficiently shews. How frequently have men of eminence perplexed and darkened the subjects they discussed, by pretending to give demonstrations of things which were self-evident, and by attempting to define that which admits of no explication! They have often presented to us the first principles of human knowledge in the form and language of mathematical demonstration; and we have found, after following their reasonings, that our ideas respecting them were not more accurate, nor our impressions of their truth stronger, than before. Nor can I help remarking in this place, that the mode of arraying moral science, whether elementary or otherwise, in the dress appropriated to pure mathematical truth, is worse than puerile, since it tends to confound, especially in the minds of the uninitiated, kinds of evidence so very different, and to impair, it is probable, in such cases, the impressions which moral evidence alone makes on the human mind. I proceed now to make a few observations on some terms which frequently occur in inquiries connected with Moral Philosophy; and which, though they may already be familiar to us, require, from the important facts and truths with which they are connected, a clear elucidation.

1. The word law very frequently occurs in the

*Reid's Essays, vol. i. ch. i.

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sciences both of matter and of mind. Philosophers speak of the law of gravitation, and of the laws of thought; when they only mean to state certain established facts connected with the intellectual and material phenomena. In the proper sense of the word, a law is a rule given to an agent, according to which he is to act; which implies a power of conforming to the particular mode required;-without this agent, and this power, a law is obviously nothing, and can do nothing. There can be no objection, however, to the use of the term, as applied to the order of nature, whether in matter or in mind, provided we always remember that in such an acceptation its meaning can only be, that uniform mode of acting by which it pleases the Deity to govern the world. When we find, wherever our observation extends, that matter invariably gravitates towards a given centre, we are in the possession of a fact, which whether it be produced immediately by the efficiency of the Creator, or by some intervening cause, must be regarded as the result of his appointment, and which must, therefore, be that particular species of arrangement which is most conducive to the harmony of the universe. When we denominate such a fact by the term law, it is understood that we refer it to the appointment of God.

2. The word nature merits our notice, on account of the frequency of its occurrence, and the extreme vagueness and ambiguity of its application. It usually means the constitution and appearance of things: it is sometimes used to denote universal existence, as, when we say that it is not in the compass of nature

In a more restricted sense it is employed to signify the native state or properties of any being or substance; and by philosophers it is frequently used to denote the almighty Being, by whom the universe is governed. The plea which has been urged for its use in this latter acceptation is, that it prevents the frequent repetition of the name of God; and that scientific men may, therefore, allude to his attributes and his efficiency, as displayed in the formation and appearance of the world, without seeming irreverence in the use of those sacred appellations by which, in revealed religion, he has made himself known. How far this plea is valid, I shall not take upon me to determine: the principle upon which it is founded-profound reverence for the name of the Creator,cannot be too strongly recommended, or too closely adhered to by those who direct their attention to philosophical inquiries. At the same time, the practice which it defends is so liable of abuse, and so capable of being employed in diverting the mind from the great Author of all things, that it should be followed, not only with much caution, but with some limitation.

3. Induction is a word which is in frequent use in modern science: that operation which it is employed to signify is one of the most essential to the furtherance of knowledge. We have a notion of its nature, sufficiently accurate, in the following words: when from a comparison of a number of facts known from experiment or observation to be true, the existence of a more general fact is inferred, the inference is said to be made by induction. That it is from induction alone that all certain and accurate knowledge