ABSTRACT. — In this talk I will develop a semantics for merely expressive devices: linguistic expressions that help us to express propositions (thoughts) but which do not at the same time contribute to the truth conditions of the propositions thereby expressed. Logical operators constitute paradigm case examples of such merely expressive devices, but I will argue that there are many further merely expressive devices, including stipulatively defined terms and metaphysical modalities. Ultimately, the semantics will throw new light on various important philosophical debates, such as on the viability of analyticity and the metaphilosophical status of logic and metaphysics. Moreover, the semantics will explain why there are no boundaries to the viability or control of the conceptual engineering of merely expressive devices, for the simple reason that “the world“ does not contribute to their meaning.