Final answer:
Gertrude perceives Hamlet's extreme emotional expression as madness because it surpasses rational or objective explanation, making it seem irrational and disproportionate to the events as they appear.
Step-by-step explanation:
Gertrude believes Hamlet's words and conduct indicate insanity because his emotions exceed the bounds of the actions available to him. Within the framework of Shakespeare's Hamlet, Gertrude perceives her son's erratic behavior, such as his repetitive speech and puns, not as a calculated ruse but as a manifestation of extreme emotion that finds no appropriate expression in action.
Hamlet is consumed by disgust, particularly towards his mother, Gertrude, which is too vast and inexpressible to be entirely feigned or understood. Thus, Gertrude's interpretation of madness stems from the fact that Hamlet's displayed emotions do not seem to have a direct objective equivalent or rationale, making them appear irrational or insane to her.
Gertrude believes that Hamlet's words and conduct indicate insanity due to his unusual behavior, such as his repetition of phrases, puns, and levity.
These actions are not part of a deliberate plan, but rather a form of emotional relief. Hamlet's intense and inexpressible feelings, which exceed their object, contribute to Gertrude's perception of him as insane. Shakespeare's portrayal of Hamlet's emotional turmoil and his inability to find an outlet for his emotions creates a character that Gertrude interprets as mentally unstable.