I've heard it said that Mace made the right decision to kill Sidious in front of a conflicted Anakin, but looking at what info we have I don't see how anyone can reasonably claim this. Lucas knew what he was doing, the scene doesn't exist in a vacuum - most notably inverting Luke's compassionate decision not to kill Vader in ROTJ - and Lucas didn't have Mace's action attempted by an influential and leading member of the Jedi (spiritually and politically) by coincidence. Lucas states on the commentary "Mace was going to arrest him but after Palpatine did the lightning he changed his mind." and "Mace should have arrested Palpatine." Note "should have" implies he is not referencing Mace's earlier arrest attempt, but reinforcing even after the lightning attempt Mace still would be making the correct decision in arresting Sidious. To me it implies despite Sidious resisting violently at first, if Mace attempted another arrest when Palpatine feigned weakness Palpatine would have gone quietly for now, if only to fool Anakin. He was counting on Mace doing what he did, he was provoking Mace to achieve that exact response. I feel Mace is making a partially emotional decision here, going against the Jedi teachings. Logically the only thing that has changed about Palpatine's position since the fight is that Palpatine has attacked him repeatedly and pissed him off, but Mace does a 180 on his initial decision to arrest. "He has control of the Senate and the Courts" was already true before, and is arguably just rationalisation to do something Mace deep down knows goes against his own philosophy. I can't see Mace's actions as purely logical. He is right that Palpatine would likely ultimately turn an arrest to his advantage, but it would buy them time to get any support from the Senate - the way it plays out they didn't acquire any approval whatsoever. Mace even states to himself in the novelisation his one attachment is the Republic. He fears the loss of democracy and the Jedi Order and it colours his actions. His fears are pretty founded, yes, but I think it is pretty contradictory to respect and believe in the Jedi way yet gloss over Mace making a clearly emotion based decision, something the Jedi are of course majorly trained not to do. There is a lot to link the scene to ROTJ's climactic confrontation. Emperor (ROTJ): "Young fool. Only now, at the end do you understand." Mace (ROTS script): "You old fool. The oppression of the Sith will never return. You have lost." Emperor (ROTJ): "So be it... Jedi." (Jedi is said with contempt reflecting a personal grudge in the Emperor). Mace (ROTS script): "You Sith disease. I am going to end this once and for all!" (Again, Sith mentioned as a sign of personal hatred from Mace). More directly; Mace's lack of clarity regarding Anakin's conflict... and trying to kill Palpatine, despite the chosen one's presence and Anakin's compassion for Palpatine, is a symbolic echo of Palpatine's blindness to Vader's conflict in ROTJ. Punctuated by The Emperor trying to kill Anakin's only link to his past in his son right in front of a conflicted Vader. At both climaxes the ones closest to Anakin/Vader by association (Jedi Master/Sith Master) were spiritually the furthest away. In the novelisation, Mace senses when Anakin arrives that Palpatine's shatterpoint is that Palpatine trusts Anakin, but doesn't realise what it means. He thinks he senses Palpatine's fear and that it means Palpatine is about to be defeated, but indicated by Palpatine's retort; the fear Mace is blind to the source of is Anakin's. From the novel... "Save your twisted words, my Lord. There are no politicians here. The Sith will never gain control of the Republic. It's over. You've lost." Mace leveled his blade. "You lost for the same reason the Sith always lose: defeated by your own fear." Palpatine lifted his head. His eyes smoked with hate. "Fool." he said. He lifted his arms, his robes of office spreading wide into raptor's wings, his hands hooking into talons. "Fool!" His voice was a shout of thunder. "Do you think the fear you feel is mine?" The climax of the scene in the novelisation: "I . . . can't. I give up. I ... I am too weak, in the end. Too old and too weak. Don't kill me, Master Jedi. Please. I surrender." Victory flooded through Mace's aching body. He lifted his blade. "You Sith disease --" "Wait--" Skywalker seized his lightsaber arm with desperate strength. "Don't kill him--you can't just kill him, Master--" "Yes, I can." Mace said, grim and certain. "I have to." "You came to arrest him. He has to stand trial--" "A trial would be a joke. He controls the courts. He controls the Senate--" "So are you going to kill all them, too? Like he said you would?" Mace yanked his arm free. "He's too dangerous to be left alive. If you could have taken Dooku alive, would you have?" Skywalker's face swept itself clean of emotion. "That was different--" Mace turned toward the cringing, beaten Sith Lord. "You can explain the difference after he's dead." He raised his lightsaber. "I need him alive!" Skywalker shouted. "I need him to save Padme!" Mace thought blankly, Why? And moved his lightsaber toward the fallen Chancellor. Before he could follow through on his stroke, a sudden arc of blue plasma sheared through his wrist and his hand tumbled away with his lightsaber still in it and Palpatine roared back to his feet and lighting speared from the Sith Lord's hands and without his blade to catch it, the power of Palpatine's hate struck him full-on. He had been so intent on Palpatine's shatterpoint that he'd never thought to look for Anakin's. Dark lightning blasted away his universe. He fell forever. Both Anakin's Jedi Master (ROTS) and Vader's Sith Master (ROTJ) are overconfident in their victory at the crucial moment. And both trust Anakin - Mace; finally, because Anakin's mission to spy on Palpatine appears successful, and The Emperor; because he believes once turned a Sith will never stray from the dark.