1984 is all about rebellion. Winston starts a diary for rebellious thoughts. He then becomes concerned with grand-scale, organized resistance to the Party’s rule, and joins the Brotherhood. Julia contents herself with private acts of rebellion, by engaging in sex and wearing makeup. Either way, Winston and Julia are not content with conformity to the Party’s rule or principles. And the Party devotes substantial resources to detecting rebellion and subversion.
As exemplified by the fact that the Party’s impossible doctrines drive Winston and Julia to engage in rebellious acts, an overly oppressive state power often causes rebellion by giving its constituents the very causes for rebellion. This is the Party’s fatal flaw.
Winston and Julia’s love for each other is a more dangerous form of rebellion than their sexual relations are.