Capital and Interest (German: Kapital und Kapitalzins) is a three-volume work on finance published by Austrian economist Eugen Böhm von Bawerk (1851–1914).
In this work Böhm-Bawerk built upon the time preference ideas of Carl Menger, insisting that there is always a difference in value between present goods and future goods of equal quality, quantity, and form.
Secondly, people have a tendency to underestimate their future needs due to carelessness and shortsightedness.
Book III, Value and Price, built on Menger's Principles to present a distinctly Austrian version of marginalism.
To illustrate marginalism, he gave the following example: A pioneer farmer had five sacks of grain, with no way of selling them or buying more.
Instead of reducing every activity by a fifth, the farmer simply starved the parrots as they were of less utility than the other four uses, in other words they were on the margin.