Final answer:
Winston Smith does not explicitly write his diary for any high-ranked Party member in George Orwell's '1984', but he mentally dedicates it to O'Brien as a potential intellectual equal. Writing the diary is an act of rebellion symbolizing his struggle against the oppressive regime.
Step-by-step explanation:
The high-ranked Party member for whom Winston is writing his diary in George Orwell's 1984 is not explicitly stated; Winston writes his diary for himself as an act of rebellion and secret defiance against the Party. At no point does he write the diary for a higher-ranked member such as Big Brother, O'Brien, Emmanuel Goldstein, or Julia.
However, Winston does contemplate that if he was writing it for anyone, it would be for O'Brien, whom he sees as an intellectual equal and later develops a complicated relationship with. But this is a private thought rather than an actual dedication to O'Brien.
In 1984, Orwell creates a world to warn readers about the dangers of totalitarianism, a theme reflected in the oppressive surveillance state that actively suppresses free thought and individualism. While Winston serves the Party, he preserves his innermost thoughts and dissents in his diary, a crucial narrative device that exposes the protagonist's true feelings against the oppressive regime.
The act of writing secretly and the thoughts contained within the diary are among the forms of resistance that illustrate the struggle for autonomy and truth within a totalitarian system.