Is thinking that because he or she has not been bested at the door that this is a point in his or her favor that they have the "Truth". What this thinking fails to take into account is that people are self-motivated and unless there is some compelling psychological payoff or some monetary payoff in making the sort of investment required to "defeat" the Witness argument,(Which rarely involves the whole) that they will rarely be engaged except by the few who haven't the mental acumen to understand what constitutes a worthwhile investment.
The JW leaves with unwarranted satisfaction on these occasions imagining that this encounter is one more implicit vote in favor of "the Truth"