“The thief,” said G., “is the Minister D——, who dares all things, those unbecoming as well as those becoming a man. The method of the theft was not less ingenious than bold.
While describing the theft of the letter, the prefect reveals Minister D–– to be the perpetrator of the crime. This introduction to Minister D–– is interesting. The idea that he dares things that are both becoming and unbecoming suggests that he is daring in ways that are generally praised, but he lacks the moral boundaries to curb that daring. In other words, there’s nothing Minister D–– won’t do. This description prefigures Dupin’s later assessment of Minister D–– as “an unprincipled man of genius.” Because Minister D–– lacks principles, there is no limit on the chaos he can create.
His lynx eye immediately perceives the paper, recognises the handwriting of the address, observes the confusion of the personage addressed, and fathoms her secret.
This quotation comes from the prefect’s description of the theft. In a short sentence, the prefect here conveys that Minister D–– has an analytical mind on par with Dupin’s. He is observant, with cat-like vision, noticing the letter the royal lady has attempted to hide in plain sight. Recognizing the handwriting and noticing the royal lady’s discomfort, he realizes that she doesn’t want the letter discovered. He uses this understanding of the situation to steal the letter. Thus, Minister D–– is not merely bold, but he has the mind necessary to make use of that boldness.