Under progressive marking, telic predicates can describe events that fail to reach culmination. Prominent accounts of this so-called "imperfective paradox" tie the effect to the modal accessibility of culmination, intensionalizing the progressive operator so that it instantiates qualifying (culminated) eventualities across a set of alternatives to the evaluation world. This approach faces a number of empirical challenges, including the acceptability of progressives of unlikely or locally out-of-reach events. This paper proposes a new approach, on which telic progressives are instead sensitive to (mereological) structure inherited from an event type associated with telic predicate P. An event type constitutes a formal causal model (e.g., Pearl 2000) in which P's culmination condition C occurs as a dependent or caused variable.  The model provides a set of causal pathways for realizing C, each of which comprises a set of jointly sufficient causal conditions for C, and also establishes (sets of) conditions which preclude C. On this approach, the progress of an actual token P-eventuality can be measured with respect to the event type. A reference time situation s satisfies PROG(P) just in case it is a plausible cross-section of an incomplete causal pathway in P: s must verify some but not all the conditions in a causal pathway for C, and fail to verify a sufficient set of conditions for non-culmination.