The principles of investment are involved in activities that do not pass through the marketplace, and are not normally thought of as economic. Putting things away after you use them is an investment of time in the present to reduce the time required to find them in the future. Explaining yourself to others can be a time-consuming, and even unpleasant, activity but it is engaged in as an investment to prevent greater unhappiness in the future from misunderstandings.
Thomas Sowell, Basic Economics, 4th ed. (2010), Ch. 12. Investment and Speculation
