2+2=5

Lyrically, he is talking about oppression. Throughout the song, he says things like "where two and two always make five", and "hail to the thief". Allusions such as these to 1984 by George Orwell have connotations of extreme oppression.

The sound of the song in addition to the singer's dark voice gives off a fearful submissive sound. Just hearing the song makes me feel like the singer has given up.

In 1984, The concept of 2+2=5 is symbolic of the inability to control one's life. In 1984, the party makes people believe anything, even obvious lies like 2+2=5. The singer is using this allusion to describe his thoughts on this type of extreme oppression.