Non-deterministic Matrices and Modular Semantics of Rules Arnon Avron Abstract We show by way of example how one can provide in a lot of cases simple modular semantics of rules of inference, so that the semantics of a system is obtained by joining the semantics of its rules in the most straightforward way. Our main tool for this task is the use of finite Nmatrices, which are multi-valued structures in which the value assigned by a valuation to a complex formula can be chosen non-deterministically out of a certain nonempty set of options. The method is applied in the area of paraconsistent logics with a formal consistency operator (knowns as LFIs), allowing us to provide in a modular way effective, finite semantics for thousands of different LFIs.