In 1984, how is there more truth in freedom than in lies?

In Part One, Chapter Seven, of 1984, Winston outlines his belief that there is more freedom in truth than in lies. He demonstrates this through the following quote:

Freedom is the truth to say that two plus two equals four.

What Winston means here is that the Party's power is based on the denial of individual thought and action. They rewrite history, for example, and have invented their own language called Newspeak. The Party also tells people who to hate, through the Two Minutes Hate, and forbids dating and sexual relationships between Party members.

For Winston, then, the Party is so manipulative that it can make people believe anything it tells them. If the Party says, for instance, that two plus two equals five, people must believe it, even though it is wrong. Failure to accept the Party's version of the truth results in accusations of thoughtcrime and imprisonment in the Ministry of Love, as we see in Part Three of the novel. 

So, for Winston, being able to express individual thought, like saying that two plus two equals four, is the essence of true freedom.