The purpose of this paper is to provide a plausibility argument for a new way of thinking about intra-personal morphosyntactic variation. The idea is embedded within the framework of the Minimalist Program, and makes use of notions of feature interpretability and feature checking. Specifically, I argue that underspecification of uninterpretable features in a matching relation with interpretable features allows us to model categoricality and variability within a single system. Unlike many current approaches to intra-personal variation (which involve multiple grammars or building stochastic weightings into the grammar itself), the system attempts to predict (rather than capture) frequencies of variants. It does this by combining an evaluation metric for the acquisition of uninterpretable features with the standard properties of features and syntactic operations in the Minimalist framework. The argument is made through a case study of was/were variation in a Scottish dialect.