Final answer:
The theme of Hamlet's soliloquy in Act IV, scene 1 is the contemplation of life and death.
Step-by-step explanation:
The theme of Hamlet's soliloquy in Act IV, scene 1 is the contemplation of life and death. In this soliloquy, Hamlet reflects on the nature of human existence and the fear of what comes after death. He discusses the value of life and the fear of the unknown, questioning whether it is better to live or die. Hamlet's soliloquy highlights his internal struggle and his deep thoughts on mortality.