In proceeding to give my reasons for adopting the opinion of Adam Smith with the modification above suggested, I shall first endeavour to show that some such classification of the different sorts of labour is really called for in an inquiry into the causes of the wealth of nations, and that a considerable degree of confusion would be introduced into the science of political economy by an attempt to proceed without it. We shall be less disposed to be disturbed by plausible cavils, or even by a few just exceptions to the complete accuracy of a definition, if we are convinced that the want of precision which is imputed to it, is beyond comparison less in amount and importance than the want of precision which would result from the rejection of it.
In the first place, then, it will readily be granted, that as material capital is the specific source of that great department of the national revenue, peculiarly called profits, and is further absolutely necessary to that division of labour, and extended use of machinery, which so wonderfully increases the productive powers of human industry, its vast influence on the progress of national wealth must be considered as incontrovertibly established. But in tracing the cause of the different effects of the produce which is employed as capital, and the produce which is consumed as revenue, we shall find that it arises principally from the different kinds of labour directly maintained by each. It is obvious, for instance, that it is only the productive labour of Adam Smith, which can keep up, restore, or increase, the material capital of a country. It is also this kind of labour alone, that is, the labour which is realized in the production, or increased value of material objects, which requires a considerable amount of capital for its continued employment; but that, for which there is an effectual demand, will generally be supplied, and the practical consequence is such as might naturally be expected. In those countries which abound in the number, and especially in the skill of their productive labourers,
