Did Winston know that OBrien was a part of the Party or not?

The answer to this
is not a straightforward one. Initially,does not know thatis really working on behalf of the
Party. This is shown by the fact that he visits his apartment and receives from him a copy of
Goldstein's book. In addition, in , when Winston is imprisoned in the Ministry of Love, he
wonders if O'Brien has also been caught and arrested. When O'Brien finally visits Winston in his
cell, Winston says:

"Theyve got you too!" he
cried.

This shows that Winston has no idea that O'Brien
works for the Party. However, in the next paragraph, Winston admits that deep down, he always
knew that O'Brien was working for the Party:

Yes, he saw
now, he had always known it.

This suggests that instead
of realizing that O'Brien really was a member of the Inner Party, working on behalf of Big
Brother, Winston allowed himself to be lulled into a false sense of security. Why? Because
Winston was desperate to rebel. He so badly wants to bring down Big Brother that he lets it
cloud his judgment. He chooses to believe in O'Brien, the Brotherhood, and Goldstein's book
instead of realizing that he could never overcome a force as strong as the
Party.