When Yeats describes his subject 'pilgrim soul' he reveals his love for HER YOUTH AND BEAUTY.
William Butler Yeats is the author of the poem 'When You Are Old', which talks about his love for a former lover. The poem is made up of three stanzas and each stanza has four lines. The poem reveals that even though the author loved his lover completely she refused his love and ended up marrying another man. The author fell completely for his former lover because of her youth and beauty.