Brutus’ act 2.1 soliloquy reveals the flawed reasoning that he’s using to defend the assassination plot. He assumes that Caesar’s growing power will result in forming a tyrant, but Brutus already considers Caesar a tyrant. He is struggling to find just cause or at least an honorable reason to undertake such a heinous act. He concludes that it is for the good of Rome.
This website can help you formulate a response, it has what happens with brutus in that scene: http://www.shmoop.com/julius-caesar/act-2-scene-1-summary.html
