The earliest work by Ludwig von Mises on uncertainty that I can think of is in the English edition of Human Action (1949) in Chapter VI, long after Keynes had published “The General Theory of Employment,” Quarterly Journal of Economics 51 (1937): 209–223.
Both Keynes and Frank Knight came to their views on uncertainty largely independently without any influence from Mises, as far as I am aware.
Frank H. Knight’s Risk, Uncertainty and Profit (Houghton Mifflin, Boston) was published in 1921. I see no evidence Knight was influenced by Mises. Curiously, in the introduction to the scholar’s edition of Human Action, we have this account of Mises’s inspiration for the chapter on uncertainty:
“Several commentators have noted the similarity of Mises’s distinction between class probability and case probability and that between risk and uncertainty introduced by Knight in Risk, Uncertainty and Profit in 1921.But the idea that Mises was not influenced by Knight in regard to his chapter on uncertainty rings hollow to me. If Mises had been “long familiar with Knight’s work” and actually cited it in Nationalökonomie (first published in Geneva in 1940), then the view that there was some influence from Knight on Mises’s thinking on uncertainty seems plausible.
Yet, it does not appear that Mises was influenced by Knight in this regard. Mises had been long familiar with Knight’s work, and had already made reference to Risk, Uncertainty and Profit in Nationalökonomie in conjunction with his discussion of profit and uncertainty.
Rather, it appears more likely that Mises’s Chapter VI was stimulated and influenced by his younger brother, Richard von Mises (1883–1953). A professor of aerodynamics and applied mathematics at Harvard University, Richard von Mises’s most outstanding theoretical achievement was his contribution, from 1919 onward, to the frequency theory of probability. In principle, Ludwig accepted Richard’s frequency interpretation of probability, but Ludwig provided a new definition of randomness, and thus significantly improved on Richard’s theory. (Mises 1998: xvi).
Knight, F. H. 1921. Risk, Uncertainty and Profit, Houghton Mifflin, Boston.
Mises, L. 1940. Nationalökonomie, Theorie des Handelns und Wirtschaftens, Éditions Union, Geneva.
Mises, L. 1998. Human Action: A Treatise on Economics. The Scholar’s Edition, Mises Institute, Auburn, Ala.
Keynes, J. M. “The General Theory of Employment,” Quarterly Journal of Economics 51 (1937): 209–223.