Shakespeare's speaker, who begins with a most ceremonial tone in the first lines, expresses awe and firm conviction regarding the power of intellectual/spiritual love.
Let me not to the marriage of true minds
In this sonnet, the speaker argues that the ideal romantic love is one that conjoins body and soul. For true love surpasses the corporeal, the "rosy lips and cheeks" and the temporal, the"brief hours and weeks"; indeed, it remains constant and eternal "even to the edge of doom."
Furthermore, there is an earnestness to the tone of the speaker as he expresses this profound sentiment. Indeed, his emotional insistence suggests that if he can succeed at his argument that a spiritual love supercedes time and is steadfast through eternity, he strengthens the puissance of his own feelings and may well capture the mind and heart of his beloved.