Because he is alone in having memories, it makes him question the reliability of his memories. Memories are easily influenced by the Party and the media, and is a key factor in maintaining their power. As long as the people live in a perpetual present, with no memory of the past and no hope for a future, they will maintain under the Party's control. Orwell uses this to show the effect of media and propaganda in totalitarian systems. When the line between truth and fiction is blurred, there is no recollection of true memories. Without memories, the people only have the Party to rely on for information, which they alter according to the present, this is what Winston does for a living. (As someone who's job is to rewrite the past, Winston, unlike his peers, is always questioning the truth of what he hears and sees and his goal is to seek the ultimate truth