Conceptually (see also The Fundamental Relations of Syntax and Conceptual Structure) the head of each sentence is a predicate. The predicate combined with its arguments to form a basic eventuality.

In today’s lecture I shall walk you through the process of reading an essay for its argumentative structure. I asked you try to identify the article’s thesis statement for today’s lecture. This is the ...

The structure of a text is the sequence of ideas ... These will often be presented in stages or with several twists and turns of argument. The ending generally sums up the main idea of the text ...