 In more detail, suppose an agent has degrees of belief \(p(i)\) that the outcome of a SIC on a system would be the \(i\)th, and degree of belief \(r(j\mathbin{|}i)\) in the \(j\)th outcome of an actual measurement \(M\) conditional on the \(i\)th outcome for the hypothetical SIC on that system. Then QBists take Equation \((\ref{ex2})\), stating a condition on the agent’s degree of belief \(q(j)\) that the outcome of \(M\) will be the \(j\)th, as their preferred formulation of the Born Rule. In this expression \(d\) stands for the dimension of the system’s Hilbert space (assumed to be a positive integer).