 While this norm is synchronic in that it constrains your credences at each time, the next norm is diachronic. Suppose that you just received a piece of evidence E, which is true in at least some possibilities under consideration. Suppose further that E exhausts all the evidence you just received. Then the Principle of Conditionalization says that your credences ought to change as if you followed the procedure below (although it is possible to design other procedures to the same effect):