Although this is a question solely of nomenclature, it is one of sufficient importance to be worth another attempt to settle it satisfactorily. For, although writers on political economy have not agreed in the ideas which they were accustomed to annex to these terms, the terms have generally been employed to denote ideas of very great importance, and it is impossible that some vagueness should not have been thrown upon the ideas themselves by looseness in the use of the words by which they are habitually designated. Further, so long as the pedantic objection to the introduction of new technical terms continues, accurate thinkers on moral and political subjects are limited to a very scanty vocabulary for the expression of their ideas. It therefore is of great importance that the words with which mankind are familiar, should be turned to the greatest possible advantage as instruments of thought; that one word should not be used as the sign of an idea which is already sufficiently expressed by another word; and that words which are required to denote ideas of great importance, should not be usurped for the expression of such as are comparatively insignificant. The phrases _productive labour_, and _productive consumption_, have been employed by some writers on political economy with very great latitude. They have considered, and classed, as productive labour and productive consumption, all labour which serves any _useful_ purpose--all consumption which is not _waste_. Mr. M'Culloch has asserted, _totidem verbis_, that the labour of Madame Pasta was as well entitled to be called productive labour as that of a cotton spinner. Employed in this sense, the words _productive_ and _unproductive_ are superfluous, since the words _useful_ and _agreeable_ on the one hand, _useless_ and _worthless_ on the other, are quite sufficient to express all the ideas to which the words _productive_ and _unproductive_ are here applied. This use of the terms, therefore, is subversive of the ends of language. Those writers who have employed the words in a more limited sense, have usually understood by productive or unproductive labour, labour which is productive of wealth, or unproductive of wealth. But what is wealth? And here the words productive and unproductive have been affected with additional ambiguities, corresponding to the different extension which different writers have given to the term wealth. Some have given the name of wealth to _all things_ which tend to the use or enjoyment of mankind, and which possess exchangeable value. This last clause is added to exclude air, the light of the sun, and any other things which can be obtained in unlimited quantity without labour or sacrifice; together with all such things as, though produced by labour, are not held in sufficient general estimation to command any price in the market.