The following metaphor appears in "Self-Reliance:" "These are the voices which we hear in solitude, but they grow faint and inaudible as we enter into the world." In this metaphor, one's inner voice becomes so soft that we cannot hear it when we are in society. "Voices" stand for our conscience, for what we know is right. When we are swayed by what others think is right, we lose our internal compass. Emerson's essay as a whole is about the importance of listening to one's conscience and following it. He believes that society corrupts this innate sense of what is good and right and that each person must make this determination for him or herself by cultivating and listening to his or her inner voice. Greatness is never achieved, Emerson believes, by copying others; instead, it consists of cultivating what is innate and good in oneself.
At the heart of Emerson's famed essay, "Sel-Reliance," is the line,
Every heart vibrates to that iron string.
The metaphor of "iron string" is the innate independence of man which Emerson has established as intrinsic to man earlier in his essay as he alludes to man's infancy and youth which conforms to no one and expresses his young man without compunction. The voice of independence, Emerson further contends, is that which we hear in solitude, but is quieted by society that is "in conspiracy" against the individual who threatens the security of its culture and power. Thus, society creates fear in an individual, demanding that he conform. This conformity, however, works against the "iron string" that is inherent in any man.
Therefore,"Whoso would be a man must be a non-conformist" Emerson insists. Indeed, man must respond to the "iron string" of his heart and soul--his transcendent destiny of individualism is he is to live an authentic existence.