The source illustrates the affirmative construction as follows:
«بالضرورة كل كاتب متحرك الأصابع ما دام كاتبا لا دائما»
Necessarily every writer moves the fingers while writing, but not permanently.
Its parts are:
Subject: writer.
Predicate: one whose fingers move.
First judgment: necessity of movement while the writing description applies.
Second qualification: the movement is not lifelong.
This is called affirmative because the first part affirms movement. The example is part of the book's conceptual teaching model rather than a claim that every possible mode of writing physically requires finger motion at every instant.