In The Sign of Four, the main characters Dr. Watson and Sherlock Holmes both resemble two different worlds, one that is emotional, alive and full of pleasure, and one that is dull and strongly focused on one's duties. There seems to be an imaginary wall that separates these two polar characters, a wall alike to the one mentioned in Robert Frost's poem "Mending Wall." In both literary works, two individuals exist, each on opposite sides of the wall, to symbolize their different outlooks on life. On one side of the wall is the individual who seeks to live a three-dimensional lifestyle full of love, friendship, hardship, and deceit; on the other side is the individual who seeks only for duty and purpose in life--one that looks at life in a methodological and banal fashion.
The interaction of these two opposite worlds and the different ways that they perceive the world creates two distinct outlooks on life and brings about a huge paradox on the way life should be lived. .
"Detection is, or ought to be, an exact science, and should be treated in the same cold and unemotional manner. You have attempted to tinge it with romanticism, which produces much the same affect as if you worked a love-story or an elopement into the fifth proposition of Euclid." (137) Sherlock Holmes is a very dull character and views life in a direct sense. He believes that the only purpose in life is to stimulate his mind with "brainwork." And even when there is no work at hand, he must continue to stimulate his mind through the usage of cocaine. The neighbor in "Mending Wall" perceives life in the same direct fashion as Holmes. He wishes to live life in seclusion, without any human interaction and avoids any attempt at conversation with his neighbor, Frost. Both Frost and Watson perceive life oppositely. Both characters believe that there is more to life than work, and one should enjoy in other activities, as well as other people's companies.