And I have known the arms already, known them all—
Arms that are braceleted and white and bare
[But in the lamplight, downed with light brown hair!]
Is it perfume from a dress
That makes me so digress?
Arms that lie along a table, or wrap about a shawl.
And should I then presume?
And how should I begin?
Again, we see Prufrock "extensive experience" in life with the repetition of 'known them all". His relation to women as "arms" is used to illustrate his sense of experience. He feels he has seen what all variations of women have to offer. Until under the lamplight, he encounters something exclusive to this individual. The lamplight may hold some relation to the evening walk through the street. He is unaware what feature of this woman that strays his attention away from what he feels is important. Prufrock doesn't have the slightest idea on how to address the question.