We shall study the dynamical properties of an economic system with memory, populated by heterogeneous agents (workers and capitalists) who, in order to take their decisions, must first form a multiple-step-forward looking forecast. The main objectives are: (i) The study of the possibility of perfect foresight endogenous fluctuations without a dominating income effect and with a relatively high elasticity of substitution between factors. (ii) The study of the possibility and plausibility of the perfect foresight assumption for the economy considered. We shall take into account both the evolutive and the eductive approaches. In the evolutive case we shall study how the structure of agents' heterogeneous beliefs, as well as the forecasting rules they employ, affect the stability properties of the stationary state. In the eductive case we shall study the problem of the rationalisability of agents' beliefs. The two approaches will then be compared.