<title>Abstract</title>This paper is one of three contributions to a symposium commenting on papers previously published by the other authors. My analysis of Chapter 3 of the General Theory is that it built a bridge between the entrepreneurs' behaviour at the microeconomic level and the closure of the system...

Keynes's principle of effective demand constitutes a pillar for Post Keynesian theories. But Keynes's presentation remains difficult to interpret, mainly because the aggregate demand function is based on entrepreneurs' expectations. The problem is, then, to demonstrate how these entrepreneurs...