According to the sociologist Kurt Lewin (169), "there is nothing more practical than a good theory." In stark contrast to the common perception of beginners and even advanced students that linguistic theory is basically a nuisance and no more than an end in itself, this quote is in fact an ideal starting-point for the present chapter of this volume, which is designed to give a sketch of major theoretical and methodological approaches in English linguistics. Linguistic theories are no less superfluous than, for example, Newton's theory of gravitation or Einstein's theory of relativity, as both, theories in linguistics and theories in physics, strive essentially for the same goal and serve the same purpose: to identify, formulate and explain a model of the underlying rules and principles of how things work in language or in the world, respectively, by means of observation and generalization.