What specifically has happened in scene iv to prompt the thoughts hamlet expresses in his soliloquy?
1. hamlet killed polonius and realized that revenge is not the proper way to operate.

2.he found out that claudius sent rosencrantz and guildenstern to have hamlet killed. hamlet now knows that he must kill claudius or be killed himself.

3.hamlet has seen that both norway and poland are willing to lose lives and money over a piece of land and that he has a much greater cause.