 The branching time logic with indistinguishability functions developed in Zanardo (1998) unifies Peirceanism and Ockhamism. The language extends the Peircean temporal logic by modal operators, and formulae are evaluated on so-called I-trees, which are trees \(\mathcal{T} = \langle T,\prec\rangle\) with an indistinguishability function \(I\) that assigns to each time instant in \(\mathcal{T}\) a partition of the set of histories passing through that instant. Whereas in the Ockhamist semantics truth at an instant is relativized to a history, in the semantics on I-trees truth at an instant is relativized to an equivalence class modulo indistinguishability at that instant, i.e. to a set of histories. Peirceanism and Ockhamism correspond to the limiting cases where the partition is trivial, that is, a singleton or a set of singletons, respectively. For details, see Zanardo (1998), as well as Zanardo (2013) and Ciuni and Zanardo (2010), where the idea is combined with elements of the stit logic of agency.