This section was titled “Speculating About Causes.” A good clause is plausible, or is both believable and persuasive. The clause should then be represented in the thesis. In other words, a good thesis statement in an essay speculating about causes makes clear exactly what causes are being proposed. Causal arguments should be sufficient and necessary as well as being a perpetuating clause.
I have never been presented with this information, though I do believe most of what was stated in this section was common sense. You don’t want to use a clause if it is not effective and doesn’t serve a purpose. A well written paper will include several strong clauses as well as an effective thesis. In my writings, I first start off with my clauses and then use them to create a thesis.