In the first stanza, she shows that if beauty and emotion did not decline and diminish, she would be affected by his offer and proposal. This shows that she is wise and aware of the mutability of emotion and beauty. Beauty and love don't remain constant. They are transient and changeable. Therefore, she is not convinced of his fanciful and unrealistic offer. She also doubts the sincerity of his emotion and the faithfulness of his speech. The shepherd is accused of telling lies. His promises seems to be too fanciful and unreasonable to persuade his beloved.