The function of Tiresias in Waste Land?

The speaker then proclaims himself to be Tiresias, a figure from classical mythology who has both male and female features (“Old man with wrinkled female breasts”) and is blind but can “see” into the future. Tiresias/the speaker observes a young typist, at home for tea, who awaits her lover, a dull and slightly arrogant clerk. The woman allows the clerk to have his way with her, and he leaves victorious. Tiresias, who has “foresuffered all,” watches the whole thing. After her lover’s departure, the typist thinks only that she’s glad the encounter is done and over.