This quote is actually a very important and significant quote that seems to perfectly characterise the government of the Party and the way that they subvert knowledge and reality through the way that the Party manages power. These words are actually the official slogan of the Party, and acts as a perfect example of doublethink, as even the meaning of words is challenged and eroded through the autocratic power of the Party. The novel shows the way that the Party rules with its iron fist by attacking the independence of its citizens' minds so that they are able to accept changes in political allegiances such as the shifting of allies that is narrated in the story. Through such techniques the Party is shown to be able to get its citizens to believe everything it states, even if logically it makes no sense. Of course the fact that the Ministry of Love is actually the body responsible for the torture of citizens and vaporising them and the Ministry of Truth is actually responsible for lies and deception serves to demonstrate this doublethink and how the Party maintains its power.
Such statements as are contained in the slogan show the manipulative and insinuating nature of the Party. Just to take one small example, war, in a sense, is peace because it is only through the state of war and continual warfare that the citizens are able to "enjoy" peace. Reality is subtley played upon and subverted as part of the Party's psychological manipulation of its citizens.