We formalize the Keynesian insight that aggregate demand driven by sentiments can generate output fluctuations under rational expectations. When production decisions must be made under imperfect information about demand, optimal decisions based on sentiments can generate stochastic...

We construct a model to capture the Keynesian idea that production and employment decisions are based on expectations of aggregate demand driven by sentiments, and that realized demand follows from the production and employment decisions of firms. We cast the Keynesian idea into a simple model...