I n first chapter of Cervantes' Don Quixote, we read of aging hero's decision turn knight errant and travel through world with horse and armour in search of adventures, following in every way practice of knights errant he had read of. A poor country gentleman, Don Quixote could not buy new equipment, so he refurbished armor of his soldier ancestors, for ages forgotten in a corner, eaten with rust and covered with mould. However, Quixote's ancestral helmet lacked a visor, a feature often mentioned in his readings. To remedy this, Quixote constructed a visor out of pasteboard and attached it to helmet with green ribbons. Then he tested it with two strokes of his sword, the first of which demolished in a moment what had taken him a week to make. So

Discusses “Quixote’s visor,” a rhetorical turn that conceals a logical gap, an appeal to frustration or necessity. Suggests that the form of Quixote’s visor, the testing of a series of possibilities, is a way of deriving logical and rhetorical inferences in response to acts of questioning. Discusses two “cousins”--Sherlock’s visor and Darwin’s visor.