Under these circumstances, it may be desirable to consider what seem to be the most obvious and natural rules for our guidance in defining and applying the terms used in the science of political economy. The object to be kept in view should evidently be such a definition and application of these terms, as will enable us most clearly and conveniently to explain the nature and causes of the wealth of nations; and the rules chiefly to be attended to may, perhaps, be nearly included in the four following:—
First. When we employ terms which are of daily occurrence in the common conversation of educated persons, we should define and apply them, so as to agree with the sense in which they are understood in this ordinary use of them. This is the best and more desirable authority for the meaning of words.
Secondly. When the sanction of this authority is not attainable, on account of further distinctions being required, the next best authority is that of some of the most celebrated writers in the science, particularly if any one of them has, by common consent, been considered as the principal founder of it. In this case, whether the term be a new one, born with the science, or an old one used in a new sense, it will not be strange to the generality of readers, nor liable to be often misunderstood.
But it may be observed, that we shall not be able to improve the science if we are thus to be bound down by past authority. This is unquestionably true; and I should be by no means inclined to propose to political economists “jurare in verba magistri,” whenever it can be clearly made out that a change would be beneficial, and decidedly contribute to the advancement of the science. But it must be allowed, that in the less strict sciences there are few definitions to which some plausible, nay, even real, objections are not to be made; and, if we determine to have a new one in every case where the old one is not quite complete, the chances are, that we shall subject the science to all the very serious disadvantages of a frequent change of terms, without finally accomplishing our object.
It is acknowledged, however, that a change may sometimes be necessary; and when it is, the natural rules to be attended to seem to be,
Thirdly. That the alteration proposed should not only remove the immediate objections which may have been made to the terms as before applied, but should be shown to be free from other equal or greater objections, and on the whole be obviously more useful in facilitating the explanation and improvement of the science. A change which is always itself an evil, can alone be warranted by superior utility taken in the most enlarged sense.
Fourthly. That any new definitions adopted should be consistent with those which are allowed to remain, and that the same terms should always be applied in the same sense, except where inveterate custom has established different meanings of the same word; in which case the sense in which the word is used, if not marked by the context, which it generally is, should be particularly specified.
I cannot help thinking that these rules for the definitions in political economy must be allowed to be obviously natural and proper, and that if changes are made without attention to them, we must necessarily run a great risk of impeding, instead of promoting, the progress of the science.
Yet, although these rules appear to be so obvious and natural, as to make one think it almost impossible that they should escape attention, it must be acknowledged that they have been too often overlooked by political economists; and it may tend to illustrate their use and importance; and possibly excite a little more attention to them in future; to notice some of the most striking deviations from them in the works of writers of the highest reputation.