Before revision:  We develop a method to study coherency and completeness conditions for linear dynamic forward-looking rational expectations models under an occasionally binding constraint. In the context of the simple New Keynesian model with a zero lower bound, this method shows that the coherency and completeness condition generally violates the Taylor principle. Rational expectations require time-varying and correlated support restrictions on the distribution of the structural shocks.
After revision:  We show that models with occasionally binding constraints are not generically coherent. Coherency requires restrictions on the parameters or on the support of the distribution of the structural shocks.