Answer:
The fat man always presents his arguments with great certainty and based on a very consistent fact. He shows that his son's choice for war was a good and happy thing. He says it with such certainty that it is impossible to doubt what he is talking about.
Step-by-step explanation:
This question is about "War", by Luigi Pirandello, where a couple has their trip spoiled by the news that their son was called up for war. They are shocked and very sad at the news, which causes intense suffering in both. However, a fat man says that his son was called to war and died, but he does not see it as a bad thing, because his son died honorably and defending the country. The fat man's argument is spoken with such certainty and veracity that no one would suspect that he is lying about it.