demand in proportion to the payments received. It is no doubt true, that the desire to enjoy the convenience or parade of personal attendance, and the advantages of legal and medical advice, has a strong tendency to stimulate industry. But though the tendency of personal services to act as a stimulus to the production of wealth be fully allowed, they can never be said directly to create it, so long as the definition is confined to material objects. Under the circumstances most favourable to their influence, their operation can only be indirect; and if we were to include under the head of productive labour, all the exertions which may contribute, however indirectly, to the production of wealth, the term would cease to have any definite and useful signification, so as to admit of being applied with advantage to an explanation of the causes of the wealth of nations. It would at once confound the effects even of production and consumption, as there is certainly no indirect cause of production so powerful as consumption.
When we consider then the difficulties which present themselves on every supposition we can make, it may fairly be doubted whether it is probable that we shall be able to find a distinction more useful for practical purposes, and on the whole less objectionable in point of precision than that of Adam Smith; which draws the line that distinguishes riches from other kinds of value, between what is matter and what is not matter, between what is susceptible of accumulation and definite valuation, and what is without either one or both of these essential properties.
Some degree of duration and a consequent susceptibility of accumulation seems to be essential to our usual conceptions of wealth, not only because produce of this kind seems to be alone capable of forming those accumulations which tend so much to facilitate future production, but because they so essentially contribute to increase that store reserved for consumption, the possession of which is certainly one of the most distinguishing marks of riches compared
