In the following group discussion, which technique is Evgeny using to better evaluate an argument?
Evgeny:
Does this author even have the authority to comment knowledgeably on the topic?

Hailie:
Well, he is a doctor so it seems that, obviously, he knows what he's talking about.

Evgeny:
Right, but does he have children of his own? How can he suggest parents make this difficult medical decision if he doesn't know what it's like to have a sick child?