This paper proposes an ontology for temporal categories in language, emphasizing causation and consequence rather than purely temporal primitives. It introduces the concept of a "nucleus," an elementary event-complex consisting of a goal event (culmination), a preparatory process, and a consequent state. Natural-language categories like aspects, futurates, adverbials, and when-clauses are argued to change the temporal/aspectual category of propositions under the control of such a knowledge representation structure. The same concept of a nucleus plays a central role in a theory of temporal reference and the semantics of tense, which is regarded as an anaphoric category. The paper argues that any manageable formalism for natural-language temporal descriptions will have to embody such an ontology, as will any usable temporal database for knowledge about events interrogated using natural language. The paper discusses the distinction between temporal and aspectual categories, arguing that propositions conveyed by English sentences can be classified into temporal or aspectual types based on tenses, aspects, and adverbials. It introduces the concept of a "culmination," an event viewed as punctual or instantaneous, and a "consequent state," which ensues. It also distinguishes between "processes" and "culminated processes," and between "point expressions" and "culmination expressions." The paper argues that tenses, aspects, and temporal/aspectual adverbials can "coerce" their inputs into different types, transforming entities of one type into others. For example, the progressive auxiliary requires its input to denote a process, while the perfect auxiliary requires its input to denote a culmination. The paper also discusses the distinction between "in-adverbials" and "for-adverbials," and how they interact with different types of events. It argues that the perfect auxiliary requires its input to be a culmination, and that the in-adverbial requires its input to be a culminated process. The paper also discusses the distinction between "tense" and "when-clauses," arguing that tense is an anaphoric category requiring a previously established temporal referent, while when-clauses bring into focus a novel temporal referent. The paper concludes that the concept of a nucleus is essential for understanding the semantics of temporal and aspectual categories in language.This paper proposes an ontology for temporal categories in language, emphasizing causation and consequence rather than purely temporal primitives. It introduces the concept of a "nucleus," an elementary event-complex consisting of a goal event (culmination), a preparatory process, and a consequent state. Natural-language categories like aspects, futurates, adverbials, and when-clauses are argued to change the temporal/aspectual category of propositions under the control of such a knowledge representation structure. The same concept of a nucleus plays a central role in a theory of temporal reference and the semantics of tense, which is regarded as an anaphoric category. The paper argues that any manageable formalism for natural-language temporal descriptions will have to embody such an ontology, as will any usable temporal database for knowledge about events interrogated using natural language. The paper discusses the distinction between temporal and aspectual categories, arguing that propositions conveyed by English sentences can be classified into temporal or aspectual types based on tenses, aspects, and adverbials. It introduces the concept of a "culmination," an event viewed as punctual or instantaneous, and a "consequent state," which ensues. It also distinguishes between "processes" and "culminated processes," and between "point expressions" and "culmination expressions." The paper argues that tenses, aspects, and temporal/aspectual adverbials can "coerce" their inputs into different types, transforming entities of one type into others. For example, the progressive auxiliary requires its input to denote a process, while the perfect auxiliary requires its input to denote a culmination. The paper also discusses the distinction between "in-adverbials" and "for-adverbials," and how they interact with different types of events. It argues that the perfect auxiliary requires its input to be a culmination, and that the in-adverbial requires its input to be a culminated process. The paper also discusses the distinction between "tense" and "when-clauses," arguing that tense is an anaphoric category requiring a previously established temporal referent, while when-clauses bring into focus a novel temporal referent. The paper concludes that the concept of a nucleus is essential for understanding the semantics of temporal and aspectual categories in language.