Dupin is, of course, the original eccentric but brilliant detective. He seems to be a very private person, though one with connections and acquaintances in many places. He prefers the darkness and the evening; darkness, he feels, is particularly conducive to reflection. He prefers to gather his information and to ponder thoroughly before any action is taken. He talks little; an hour or more of contemplative silence seems common. And, of course, he is an expert in the psychology of people of various types; indeed, he seems to be learned in a number of areas — mathematics and poetry, for example.
The Prefect, Monsieur G —— , is a contrast to Dupin. Whereas Dupin is primarily concerned with the psychological elements of the case, G —— is almost wholly concerned with physical details and evidence. G —— talks much and says little. Dupin considers things broadly, while G —— 's point of view is extremely narrow. Anything G —— does not understand is "odd" and not worth considering; for Dupin, that is a matter for investigation. G —— believes in a great deal of physical activity during an investigation, while Dupin believes in a maximum of thought and a minimum of physical exertion. Though Dupin says that the Paris police are excellent within their limitations, it is clear that G —— 's limitations are quite severe.
The personality of the unnamed narrator, the Dupin-chronicler, lies between these two extremes. Though he shares some of Dupin's tastes — silent contemplation in darkness, for example — and has some understanding of Dupin's methods, he seems psychologically closer to G —— than to Dupin. He seems to be a rather ordinary person with rather ordinary views and ideas. Thus, his assumptions and his interjections are often erroneous; he assumes, for example, that if the police have not been able to find the letter after their search, then it must be elsewhere. In his argument with Dupin about mathematicians, the narrator takes the common view and attitude toward mathematicians, a position that Dupin explicitly suggests is idiocy. In other words, the narrator is a mediator between Dupin and the reader. His reactions are similar to those of the reader, though he is somewhat less astute than the reader, so that the reader can feel superior to him. Naturally, such a narrator guides our attitudes toward Dupin, G —— , and the case. He is, for example, in awe of Dupin's abilities and methods; while the reader may maintain a more critical distance, he is guided in that direction to some degree. Finally, such a narrator determines the amount of information which a reader receives and guides the attention of the reader to the information received. In this case, the narrator tells us everything, but only as he receives it; because he did not witness the case being solved, the reader doesn't either.
