"Hah!" cried the glasses with a laugh of forced incredulity.
"Calesimon! Calesimon was an idiot!"
"Argumentum ad hominem."
"Oh, come on. The man was institutionalized."
"And genetic fallacy, too. My, my."
"Ignore him, son," said the glasses to the youth. "He's not been very well since his wife laughed at his last paper. A tree—"
"She did not laugh," interrupted the beard.
"—is a woody plant containing specialized structures, larger overall than a bush and often, as you see here [pointing] having only one trunk rather than many."
"And is this the effect of dotage or of primordial ignorance?"
"False dilemma, Mr. Logician."
"Surely you were there that day in bonehead English when they distinguished between 'definition' and 'explanation.' You are familiar with the English language, aren't you? The young man has asked for an explanation."