A note on the “unique” business cycle in the Keynesian theory

In this paper, we explore the existence and “uniqueness” of a limit cycle in a Keynesian model of business cycles. In a model with the simplest (linear) Keynesian consumption function and the logistic investment function based upon the profit principle, we establish the existence of a periodic orbit (irrespective of the speed of quantity adjustment) and verify, with the help of the theory on generalized Lienard systems, the uniqueness of it for the case in which the speed of quantity adjustment is large enough