how would a party member explain the three paradoxical party slogans?

The three slogans of the Party are "WAR IS PEACE," "FREEDOM IS SLAVERY," "IGNORANCE IS STRENGTH." The Ministry of Truth is extensively involved with news media, the entertainment industry, the fine arts and the publication of educational books. Its ultimate purpose is to rewrite history and change the facts to fit Party doctrine for propaganda effect. This rewriting not only includes the distant past, but the novel's present as well. If they make a mistake in their predicitons, they simply rewrite things again.

The statement war is peace has a dual meaning. Historically, war meant fighting the opposition; in 1984 we are fighting against ourselves. The state of perpetual war is internal, psychologically controlling, non-destructive, and it tends to keep society in tact. War brings people together....... therefore perpetual war in a society actually brings that society a permanent peace.