On (in)definite tense and aspect in Russian  Atle Grønn University of Oslo 1. Introduction The semantics of tense and aspect in natural language involves primitive rela- tions such as temporal precedence, temporal inclusion etc. The arguments (times and events) that participate in these relations can be definite (discourse old) or indefinite (discourse new). In order to implement this idea we need a dynamic framework. The framework must furthermore be compositional to account for the systematic interaction between tense and aspect. In Grønn & von Stechow (to appear) we try to bring these ingredients together in a general theory with examples mostly from English. In section 2, I will show how the system works for tenses in Russian, includ- ing embedded tenses. The idea is to present at a semi-formal, intuitive level the most important observations and facts supporting this kind of approach. For the rest of the paper, starting with section 3, I will focus on Russian as- pect and illustrate the phenomenon of (in)definite aspect with the notoriously difficult ‘factual’ reading of the Russian imperfective (Grønn 2004). I will make two principled arguments concerning the Russian imperfective: there is no uni- fied semantics for this unmarked form; in fact even the factual IPF, character- ized by the semantically perfective inclusion relation ‘e ⊆ t’, can be divided into two readings – an indefinite and a definite event reading depending on the dis- course status of ‘e’. Second, I see no principled reasons for why this complete event interpretation ‘e ⊆ t’ should be limited to past tense (e.g. the deictic past: t < now). Hence, this semantically ‘fake’ imperfective is expected to occur with other tenses, and also in non-indicative moods, whenever pragmatic reasoning enhances a ‘perfective-like’ interpretation of the imperfective.  Acknowledgements: I would like to thank the reviewers for their interesting comments and suggestions.