He was, I take it, the most perfect reasoning and observing machine the world has ever seen ... -- "A Scandal in Bohemia"
So says Dr. Watson in the first paragraph of the first Sherlock Holmes short story. He may have even believed it. Rex Stout seems to have believed it.
In 1949 article for Saturday Review, Stout wrote: “Sherlock Holmes is the embodiment of man’s greatest pride and his greatest weakness: his reason . . . He is human aspiration. He is what our ancestors had in mind when in wistful bragging they tacked the sapiens onto the homo.”
And then he added: “We enjoy reading about people who love and hate and covet – about gluttons and martyrs, misers and sadists, whores and saints, brave men and cowards. But also, demonstrably, we enjoy reading about a man who gloriously acts and decides, with no exception and no compunction, not as his emotions brutally command, but as his reason instructs.”
This assertion is beautifully stated and possibly even true, but inapplicable to Sherlock Holmes. In practice, Holmes acts out of emotion with great regularity. Think about it: He sets thieves and murderers free on several occasions out of soft-heartedness. He sends orange pips to the killers of John Openshaw in revenge. He refuses a more valuable fee and asks for a portrait of Irene Adler in return for his service to the King of Bohemia. And, most famously, he cries out and threatens Killer Evans for having shot Watson.
A great reasoner Sherlock Holmes was, but unemotional he most definitely was not.