§ I. INCOME AS A FLOW OF GOODS
The recurrence of wants
1. Satisfaction and gratification being only temporary conditions, economic wants appear in more or less regularly recurring series. Impressions are short lived, sensations are temporary, wants that have been satisfied recur. Wants recur for the same reason that they first arose. No impression on the nerves or on the senses is lasting. Man's senses were developed for the purpose of bringing him into relation with the outer world, of enabling him to survive in his struggle with the forces of nature. So, when a good has been enjoyed, the utility to that person of that thing or service for that particular moment, falls, it may be even to zero. To keep wants satisfied is impossible; we cannot do next year's reading or next week's eating now; we cannot live the life of to-morrow. The best results in reading or eating come from taking the right amount day by day. But it is a need in the life of men that wants should recur after a time, otherwise there would be no motive for action.
Series of wants and series of goods
2. The economic ideal is that this series of recurring wants should be met by a corresponding series of goods. It is evident that if a series or succession of goods varies, at different times, moments, and conditions, in its power to gratify wants, the closer the correspondence between the two series, that of wants and that of goods, the greater will be the total of gratification. We may liken man's life to a journey in which the supplies of food are gotten at the stations. If any one of these supplies fails, the traveler suffers the pangs of hunger, and if two or three supplies are at one point, they do not serve the needs of man so well as if distributed along the way. This constant inflow of goods is one of the fundamental needs of life. The savage dimly understands this need. Even the birds and the beasts adjust their lives to it either by travel or by toil. The spring and autumn migrations to new feeding grounds are the attempts of the bird to gratify this series of wants as they arise. The ant, the bee, and the squirrel anticipate, and work to fill their storehouses against the days of need.
Social and private incomes
3. Objective income consists of the additional sums of goods acquired by individuals or by society during the income period. The term national or social income may be contrasted with individual or private income in the objective sense. The nature of the acquisition of objective incomes may, in some cases, be different if viewed from the social and individual standpoints. Society, as a whole, may be said to acquire income only when goods are produced; individuals may acquire income by gift, bequest, theft, or other modes of transfer from other individuals. In many cases the two kinds of income, however, agree, the objective income of society being the algebraic sum of the goods acquired or parted with by all the individuals.
We should not understand that either social or private objective incomes include only material goods, for many utilities and labor services that never take on a material or money expression are included in either case. Indeed, we are close here to the conception of psychic income which is to be developed more fully.
Money income
Income of money is not often the same as income of things. Usually many of these subtler utilities are overlooked and omitted from the recognized money income. In this day the use of money is so common that we are sometimes led to ignore the value of things to which the money expression is not given. The money income is merely the money expression of the value of currently acquired goods, and it is the only medium through which such varied sources of gratification can be compared.