The best clue that the organizational structure of this essay is order of importance, the fact that the passage begins with the transitional phrase "first of all."
Explanation:
Order of Importance is a quite common type of organization structure which is used by many writers while writing essays, and other informational works. However, it is most importantly used for writing argumentative essays.
From the essay mentioned, we can easily figure out that this essay is about arguing whether something is impossible. The very first line of the essay begins with, ‘First of all’ which is transitional phrase and which depicts the possibility of arguing in itself.
