The numerical exactitude of business accounts and calculations must not prevent us from realizing the uncertainty and speculative character of their items and of all computations based on them.
The essential elements of economic calculation are speculative anticipations of future conditions. There is accuracy in the keeping of books. But they are accurate only with regard to these rules. The book values do not reflect precisely the real state of affairs. The proof is that the Stock Exchange appraises them without any regard to these figures.
Ludwig von Mises
Ludwig von Mises (1881-1973) taught in Vienna and New York and served as a close adviser to the Foundation for Economic Education. He is considered the leading theorist of the Austrian School of the 20th century.