What is a sketchy summary of the main points of an argument or theory called?

The term that describes a concise summary of the main points of an argument or theory is a "precis." A precis distills the essential elements of a larger work, capturing its core ideas in a clear and succinct manner without extraneous detail. This practice is common in academic writing and helps readers quickly understand the fundamental aspects of a complex discussion or theory.

In contrast, the other options denote different meanings and usages. An "outlook" generally refers to a viewpoint or perspective on a situation rather than a summary. An "abstract" often serves a similar purpose as a precis, but it typically includes a brief overview of the entire work rather than focusing solely on the arguments or theories within it. An "overview" provides a broad summary but may lack the precision and detailed focus that a precis embodies. Thus, the specificity and conciseness of a precis make it the most fitting answer in this context.