In this book, Omer Preminger investigates how the obligatory nature of predicate-argument agreement is enforced by the grammar. Preminger argues that an empirically adequate theory of predicate-argument agreement requires recourse to an operation, whose obligatoriness is a grammatical primitive not reducible to representational properties, but whose successful culmination is not enforced by the grammar. Preminger's argument counters contemporary approaches that find the obligatoriness of predicate-argument agreement enforced through representational means. The most prominent of these is Chomsky's "interpretability"-based proposal, in which the obligatoriness of predicate-argument agreement is enforced through derivational time bombs. Preminger presents an empirical argument against contemporary approaches that seek to derive the obligatory nature of predicate-argument agreement exclusively from derivational time bombs. He offers instead an alternative account based on the notion of obligatory operations better suited to the facts. The crucial data involves utterances that inescapably involve attempted-but-failed agreement and are nonetheless fully grammatical. Preminger combines a detailed empirical investigation of agreement phenomena in the Kichean (Mayan) languages, Zulu (Bantu), Basque, Icelandic, and French with an extensive and rigorous theoretical exploration of the far-reaching consequences of these data. The result is a novel proposal that has profound implications for the formalism that the theory of grammar uses to derive obligatory processes and properties.