The concept of a historical database is introduced as a tool for modeling the dynamic nature of some part of the real world. Just as first-order logic has been shown to be a useful formalism for expressing and understanding the underlying semantics of the relational database model, intensional logic is presented as an analogous formalism for expressing and understanding the temporal semantics involved in a historical database. The various components of the relational model, as extended to include historical relations, are discussed in terms of the model theory for the logic IL s , a variation of the logic IL formulated by Richard Montague. The modal concepts of intensional and extensional data constraints and queries are introduced and contrasted. Finally, the potential application of these ideas to the problem of natural language database querying is discussed.