If the user’s model is the fulcrum, the theoretical model of composing is the apogee of the trajectory of events in the main cycle of modelling, in the sense of being the high point of the discovery. This is because, once the theoretical model of composing had been expressed in formal terms, as being the system of functions “without which” communication could not take place, it led to insights about not only written communication, but other communication modes. In fact it suggested that communication systems operated in the complex kind of layering which is a feature of the critical realist ontology, with primary and secondary systems being involved. The theoretical model of writing generated insights into the nature of writing beyond what had been sought for, as well as suggesting some related hypotheses on the formation of modes and genres. Most importantly, the formulation of the theoretical model led to further refinement of the applied model so as to make sense of all composing, and not just “good” writing (as in Stages of the writing process). The refined applied model could then be tested out against further instances of actual composing.