The main themes of Sonnet 18 are:
Love: The poem is a celebration of love and the beauty of the speaker's beloved. The speaker is completely smitten with his beloved and believes that she is the most beautiful and perfect person in the world.
Nature: The speaker uses nature as a metaphor for the beauty and perfection of his beloved. He compares her to a summer day, a rose, and a jewel.
Immortality: The speaker believes that his beloved's beauty will never fade, even after she dies. He says that her beauty will be "eternal summer" and that she will "live in the beauty of her looks."
Sonnet 73 by William Shakespeare is a more somber and reflective poem. It is about the speaker's contemplation of his own mortality and the inevitability of death. The sonnet begins with the speaker saying that he is "tired with all these," meaning that he is weary of life and the world. He goes on to say that he would rather die than live in a world where everything is temporary and subject to change.
The main themes of Sonnet 73 are:
Mortality: The poem is a meditation on the speaker's own mortality and the inevitability of death. The speaker is aware that he is getting older and that he will eventually die.
Impermanence: The speaker reflects on the impermanence of life and the world. He says that everything is subject to change and decay, and that nothing lasts forever.
Desire for Death: The speaker expresses a desire for death, saying that he would rather die than live in a world where everything is temporary and subject to change.
Comparison and Contrast:
While both sonnets are by the same author, they have very different themes. Sonnet 18 is a joyous celebration of love and beauty, while Sonnet 73 is a somber and reflective meditation on mortality and impermanence. Sonnet 18 is filled with hope and optimism, while Sonnet 73 is filled with despair and pessimism. However, both sonnets are beautiful and moving works of art that offer a glimpse into the human experience.