Noname manuscript No. (will be inserted by the editor)

Received: date / Accepted: date Abstract The quantum theory of decoherence plays an important role in a pragmatist interpretation of quantum theory. It governs the descriptive content of claims about values of physical magnitudes and o¤ers advice on when to use quantum probabilities as a guide to their truth. The content of a claim is to be understood in terms of its role in inferences. This promises a better treatment of meaning than that o¤ered by Bohr. Quantum theory models physical systems with no mention of measurement: it is decoherence, not measurement, that licenses application of Borns probability rule. So quantum theory also o¤ers advice on its own application. I show how this works in a simple model of decoherence, and then in applications to both laboratory experiments and natural systems. Applications to quantum \u85eld theory and the measurement problem will be discussed elsewhere. PACS 03.65.Yz, 03.65.Ta, 01.70.+w