to what the consequences of their actions on the systems the states are assigned to might be.

Quantum Bayesianism, as originally conceived, is not merely a novel philosophical perspective on quantum theory but also an ambitious programme of re-formulating the theory in terms of probabilistic and information-theoretic notions rather than abstract mathematical ones. Such an information-theoretic re-formulation, it is hoped, might help us understand which elements of quantum theory represent physical features of the world and which others are derived from what constitutes rational reasoning of the agents using the theory. The strategy Fuchs announces for his programme is this: “Weed out all the terms that have to do with gambling commitments, information, knowledge, and belief, and what is left behind will play the role of Einstein’s \[space-time\] manifold”, namely, as he explains, “a mathematical object, the study of which one can hope will tell us something about nature itself, not merely about the observer in nature.”[^14] In what follows I shall not be concerned with the prospects and problems of this re-formulation programme for quantum theory, even though it certainly merits the attention it gets, but rather focus on the assumptions about the status of quantum observables, states and 