This paper discusses the effect of ‘Das Maynard Keynes Problem’ on thecomparison between keynesian economics and behavioral economics. In spiteof the similarity between two schools, there also exist the arguments on thefundamental differences between them. These contrast views on therelationship between Keynes and behavioral economics result from theinterpretation on the (dis)continuity of Keynes’s two books, A Treatise onProbability and The General Theory of Employment Interest and Money.Whereas the emphasis on the continuity in Keynes’s thought does not maintainthe status of The General Theory as the basis of behavioral macroeconomics,the argument for discontinuity in Keynes’s probability theory decreases thesimilarity of A Treatise on Probability with behavioral decision making theoryunder uncertainty.