The poet clearly denies that he is one of time's fools, or one who acts only for immediate satisfaction: "No, Time, thou shalt not boast that I do change." This theme of constancy is evident throughout the sonnet. After defiantly stating that he will not be duped into ending his love for the youth, the poet then philosophizes about how people perceive objects and events according to what they want to see, not what really is. The poet argues that because we live for only a brief span of time we value most what is old — that which has withstood the ravages of time and has existed much longer than any individual person — for example, the "pyramids" in line 2, which symbolize time's accumulation.
In the first two lines of the third quatrain, the poet again boldly asserts that his love is unlike these created images he just discussed: "Thy registers and thee I both defy, / Not wond'ring at the present nor the past." He then follows this assertion with an even greater boast in the concluding couplet: The one thing not affected by fortune or accident is the true vow of love. His brash statement "I will be true, despite thy scythe and thee" nicely balances the sonnet's opening line; his boast here at the sonnet's end counters time's boast at the sonnet's beginning.