Shakespeare realizes that a summer’s day may be beautiful but its beauty tacks permanence. The first eight lines present the theme of mutability as Shakespeare admits the fact that beauty is fleeting, youth is evanescent and for every mortal object decay and destruction is inevitable. The second part presents the worth and beauty of the poet’s friend and patron. Unlike the transient beauty of the summer’s day, the beauty of the poet’s friend will remain forever. The friend’s beauty will live as long as people read the sonnet written by the poet. The poet thus successfully moves on from the theme of mutability to the theme of immortality.
