Previously in this series: Menger on Requirements
Man plans for the sake of satisfying his future needs. He may not know which needs he’ll end up having; even if he did, he may not know the exact quantities of goods required to satisfy those needs. Man has foresight, but not divination.
But still he plans, using his reason and his senses to predict as best he can about his future needs.
Next in this series: Menger on Effective and Latent Requirements