We present a methodology for constructing abstractions and refining them by analyzing counter-examples. We also present a uniform verification method that combines abstraction, model-checking and deductive verification in a novel way. In particular, it allows and shows how to use the set of reachable states of the abstract system in a deductive proof even when the abstract model does not satisfy the specification and when it simulates the concrete system with respect to a weaker simulation notion than Milner’s.