ABSTRACT
Several linguistic tests were developed to distinguish aspectual classes. For example, adverbial modification with for two hours is possible with activities (John ran for two hours) but not with accomplishments (*John built a house for two years) or achievements. Temporal modification with the adverbial in two hours shows the reverse pattern. Usually only activities and accomplish ments can occur in the progressive. Expressions like *knowing the answer are
ungrammatical. But there is also a crucial difference in the behaviour of ac tivities and accomplishments with respect to their progressivised forms. From John was pushing a cart we can infer that John pushed a cart. However, the inference from John was crossing the street to John crossed the street is invalid. This phenomenon was dubbed the “imperfective paradox” by Dowty2.
