Symbolism, Imagery, Allegory
Sherlock Holmes is a sort of paragon, or model, for science and rationality. He's frequently described as "cold," "inhuman," logical, etc. The man is practically a robot at times. Holmes is the ultimate detective, with his extreme scientific detachment and logic. What's interesting is that these recurring mentions of scientific detachment aren't always that positive. Holmes is so logical and detached that he's cold and often unpleasant. The use of the word "cold" to describe Holmes may be something of a subtle critique, as well as a stated fact, on Watson's part. Holmes is more of a tool than an actual role model for people. He's the ultimate scientist/detective, but he's also more like a machine than an emotional human being at times.