In the spiritual realm, the currency--which exists in limited quantity and must be teleologically measured in the pursuit of any value--is time, i.e., one's life. Since a value is that which one acts to gain and/or keep, and the amount of possible action is limited by the duration of one's lifespan, it is part of one's life that one invests in everything one values. Ayn Rand Rand, A. (1966, 1990). Introduction to Objectivist Epistemology. Expanded second edition. New York: Meridian. p 34.