The episode concludes with the realization that while the plan was logically "sound," it destroyed the very humanity the Survey Corps fought to protect. Attack on Titan - Season 4 Episode 10 - "A Sound Argument"
: The episode highlights the growing instability of Eren, who has grown cold and detached, alarming his closest friends, Mikasa and Armin. 10 : A Sound Argument
The "sound argument" of the title refers to the cold logic that sacrificing one individual (Historia) is a necessary evil to save the nation. The episode concludes with the realization that while
: A small-scale display of the Wall Titans' power to deter world invasion. : A small-scale display of the Wall Titans'
: In a poignant flashback, Eren Jaeger vehemently refuses to let Historia be used as a "breeding tool".
If you are referring to the episode " A Sound Argument " (Season 4, Episode 10), it is a story centered on the heavy burden of duty and the erosion of hope.