 The Indifference Principle seems ask us to assign a \(1/3\) credence to each proposition in the left group \((1)\)–\((3)\) and, simultaneously, assign \(1/15\) to each one in the right group \((1')\)–\((15')\). If so, it asks us to assign unequal credences to equivalent propositions: \(1/3\) to \((1)\), and \(3/15\) to the disjunction \((1') \!\vee (2') \!\vee (3')\). That violates Probabilism.