“If the central question of the detective story concerns what knowledge is, then the business of the detective is the getting and deployment of it. The detective story is a quest, but getting possession of knowledge is only the first part of the tale. The rest of it concerns what to do with this knowledge, and so it is also a moral tale. The Detective is a shaman, a person who has acquired a valuable but dangerous stuff: knowledge, which may be used for good or evil. The Detective is an ambiguous figure, necessary to society but potentially destructive of it. He is a figure we cannot do with or do without. As with knowledge itself, the role the Detective is asked, or allowed, to play is a cultural decision.” (p.6)
“The detective is a specialized role. He embodies the context of rationality as a spokesman for the power of thought and the intelligibility of the universe, which is possibly a more important function than solving the crime. Indeed, there are successful detectives who do not solve the crime (Trent’s Last Case) and some unusually bumbling ones who perhaps will never solve anything (Gosford Park). The Detective’s place as a defender of rationality positions him in the larger conflict between rationality and intuition (the life of the emotions) which is in its modern form a legacy of Romanticism. Early on these two poles were constructed as cool and warm – slippery terms that are pejorative from one point of view and laudatory from the opposite – and assimilated to the supposed incompatibility of science and non-science, non-science being the whole rest of human endeavor fatally tainted by irrationality. …It is a fascinating (but separate) question to trace the attitude of fictional detectives toward art and religion, from the famously cold Holmes’s liking for the biolin and opera to Jacques Futrelle’s Augustus S.F.X. Van Dusen, Ph.D., LL.D., F.R.S., M.D., alias “The Thinking Machine.”
The demand for rational intelligibility carries with it constraints imposed by the concept of evidence and the investigative procedure of testing hypotheses – the scientific method. This, together with the need for the crime to actually be solved somehow, whether or not through the agency of a detective, are among the factors that established the genre once it was discovered to be a particularly satisfying mode of story telling.
As with the criminal, the Detective ought to be a single person (partners will be introduced later, and still later groups like Ed McBain’s 87th Precinct). Perhaps less obviously, just as the criminal ought to be within the immediate society, the Detective ought to be outside it – not outside society altogether as the noir detective is, but only part of the threatened group.” (p.14)
Ref: Charles Brownson (2014) The Figure of the Detective: A Literary History and Analysis. McFarland & Company, Inc. Publishers: Jefferson, North Carolina