s sort of determination seems based on pure logic, but in fact it also involves the important step of measuring the intelligence level of opponents through careful observation, an art rather than a science. Dupin explains this procedure in terms of what the boy told him:
When I wish to find out how wise, or how stupid, or how good, or how wicked is any one, or what his thoughts at the moment, I fashion the expression of my face, as accurately as possible, in accordance with the expression of his, and then wait to see what thoughts or sentiments arise in my mind or heard, as if to match or correspond with the expression (Poe 697).
Dupin says that the Paris police have failed in their search because they have not placed themselves in the position of the thief and have not tried to think as he does. If he were a different sort of thief, one less intelligent, and less imaginative, they might have found the letter through the plodding methods they have used. Indeed, he says that the thief is successful because he is a poet rather than a mathematician--it is his poetic imagination that has enabled him to outsmart the police.
That Dupin does not value ordinary reason is evident in his antipathy toward mathematics, which has the logic of pure reason. He sees the thief in fact as a man in whom is combined the mathematician and the poet, for if he were pure poet, he would have been able to fool everyone. As it is, he can only fool everyone except Dupin. Dupin's method is explained by Vincent Buranelli as follows:
Dupin wields the imaginative perception of meaningful symmetries that Poe says elsewhere is the key to both science and art. Intuition, acting amid a welter of clues, sets aside the trivia and fastens on a structure that emerges from putting the essential facts toge
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