But when this definition came to be explained, many persons were disposed to interpret "_all things_ which tend to the use or enjoyment of man," as implying only all _material_ things. _Immaterial_ products they refused to consider as wealth; and labour or expenditure which yielded nothing but immaterial products, they characterised as unproductive labour and unproductive expenditure. To this it was, or might have been, answered, that according to this classification, a carpenter's labour at his trade is productive labour, but the same individual's labour in learning his trade was unproductive labour. Yet it is obvious that, on both occasions, his labour tended exclusively to what is allowed to be production: the one was equally indispensable with the other, to the ultimate result. Further, if we adopted the above definition, we should be obliged to say that a nation whose artisans were twice as skilful as those of another nation, was not, _ceteris paribus_, more wealthy; although it is evident that every one of the results of wealth, and everything for the sake of which wealth is desired, would be possessed by the former country in a higher degree than by the latter. Every classification according to which a basket of cherries, gathered and eaten the next minute, are called wealth, while that title is denied to the acquired skill of those who are acknowledged to be productive labourers, is a purely arbitrary division, and does not conduce to the ends for which classification and nomenclature are designed. In order to get over all difficulties, some political economists seem disposed to make the terms express a distinction sufficiently definite indeed, but more completely arbitrary, and having less foundation in nature, than any of the former. They will not allow to any labour or to any expenditure the name of productive, unless the produce which it yields returns into the hands of the very person who made the outlay. Hedging and ditching they term productive labour, though those operations conduce to production only indirectly, by protecting the produce from destruction; but the necessary expenses incurred by a government for the protection of property are, they insist upon it, consumed unproductively: though, as has been well pointed out by Mr. M'Culloch, these expenses, in their relation to the national wealth, are exactly analogous to the wages of a hedger or a ditcher. The only difference is, that the farmer, who pays for the hedging and ditching, is the person to whom the consequent increase of production accrues, while the government, which is at the expense of police officers and courts of justice, does not, as a necessary consequence, get back into its own coffers the increase of the national wealth resulting from the security of property.