This article presents a heuristic for language teachers to articulate and explore their fundamental theories of and philosophical stances towards language, language learning, and language teaching. It includes tools with which teachers can interrogate those theories, weighing them up against their actual classroom practices. Through presenting data from a recent project investigating language teacher cognition and practices, it is demonstrated that language teachers vary in the extent to which they are able to articulate their theoretical and philosophical perspectives, and also in the extent that those theories reflect what they do in their classrooms. The article is intended to support language teachers in making sustained improvements to their classroom routines through a systematic approach to exploring their personal theories and stances towards their practice.