Hamlet is an indecisive character who cannot bring himself to take any course of action after his father's murder. What theme does Hamlet refer to as he analyzes why people are reluctant to take action?

As evident in this excerpt from Hamlet, " How can this player be so filled with grief and rage over Priam and Hecuba, imaginary figures whom he doesn’t even know, while I, who have every reason to rage and grieve and seek revenge, am weak, uncertain, and incapable of action?", the theme that Hamlet refers to talks about the fear about the possible outcomes of his actions and meaninglessness of life.