I'm not a young man. I'm old, tired and full of no coffee. - Raymond Chandler

But down these mean streets a man must go who is not himself mean, who is neither tarnished nor afraid. The detective in this kind of story must be such a man. He is the hero; he is everything. He must be a complete man and a common man and yet an unusual man. He must be, to use a rather weathered phrase, a man of honor — by instinct, by inevitability, without thought of it, and certainly without saying it. He must be the best man in his world and a good enough man for any world. I do not care much about his private life; he is neither a eunuch nor a satyr; I think he might seduce a duchess and I am quite sure he would not spoil a virgin; if he is a man of honor in one thing, he is that in all things. He is a relatively poor man, or he would not be a detective at all. He is a common man or he could not go among common people. He has a sense of character, or he would not know his job. He will take no man’s money dishonestly and no man’s insolence without a due and dispassionate revenge. He is a lonely man and his pride is that you will treat him as a proud man or be very sorry you ever saw him. He talks as the man of his age talks — that is, with rude wit, a lively sense of the grotesque, a disgust for sham, and a contempt for pettiness. The story is this man’s adventure in search of a hidden truth, and it would be no adventure if it did not happen to a man fit for adventure. He has a range of awareness that startles you, but it belongs to him by right, because it belongs to the world he lives in. If there were enough like him, the world would be a very safe place to live in, without becoming too dull to be worth living in.

They had Rembrandt on the calendar that year, a rather smeary self-portrait due to imperfectly registered color plate. It showed him holding a smeared palette with a dirty thumb and wearing a tam-o’-shanter which wasn’t any too clean either. His other hand held a brush poised in the air, as if he might be going to do a little work after a while, if somebody made a down payment. His face was aging, saggy, full of the disgust of life and the thickening effects of liquor. But it had a hard cheerfulness that I liked, and the eyes were as bright as drops of dew.
I was looking at him across my office desk at about four-thirty when the phone rang and I heard a cool, supercilious voice that sounded as if it thought it was pretty good. It said drawlingly, after I had answered:
“You are Philip Marlowe, a private detective?

If the mystery novel is at all realistic (which it very seldom is) it is written in a certain spirit of detachment; otherwise nobody but a psychopath would want to write it or read it.