A Theoretical Account of Futures Markets Get access J. C. R. Dow J. C. R. Dow London Search for other works by this author on: Oxford Academic Google Scholar The Review of Economic Studies, Volume 7, Issue 3, June 1940, Pages 185–195, https://doi.org/10.2307/2967406 Published: 01 June 1940

A Symposium on the Theory of the Forward Market: II. Addenda to Mr. Kaldor's Note Get access J. C. R. Dow J. C. R. Dow Search for other works by this author on: Oxford Academic Google Scholar The Review of Economic Studies, Volume 7, Issue 3, June 1940, Pages 201–202, https://doi.org/10.2307/2967408 Published: 01 June 1940

How can we know in advance whether simplifying assumptions about beliefs will make a difference in the conclusions of game-theoretic models? We define critical types to be types whose rationalizable correspondence is sensitive to assumptions about arbitrarily high-order beliefs. We show that a type is critical if and only if it exhibits common belief in some non-trivial event. We use this characterization to show that all types in commonly used type spaces are critical. On the other hand, we show that regular types (types that are not critical) are generic, although perhaps inconvenient to use in applications.