In Joseph Heller's novel "Catch-22," the phrase "Insanity is contagious" reflects the absurdity and chaos of war. The character’s experiences highlight how the irrationality of their surroundings can influence one's mental state. The relentless bureaucracy and the paradoxical rules they face create a sense of madness that spreads among the soldiers, suggesting that being surrounded by insanity can lead to a loss of sanity in oneself.

This quote underscores the idea that when people are embedded in an environment characterized by illogical and chaotic behavior, they can begin to accept such insanity as normal. It serves as a critique of the military and societal structures that perpetuate this cycle, illustrating how individuals can be driven to madness by the very systems meant to govern them. Overall, Heller presents a powerful commentary on the nature of sanity in a world rife with irrationality.