This song was premiered in San Sebastian, Spain on July 31, 2002. The song's alternative title is "The Lukewarm".

The song's title "2 + 2 = 5" recalls the symbol of unreality from George Orwell's novel Nineteen Eighty-Four. In the book, inhabitants of an authoritarian future state are made to engage in doublethink, replacing their own conscience and beliefs with those imposed from above. At the end of the novel, the protagonist's individuality is demolished, as he avows that two and two are, in fact, five. The song contains similar inaccuracies including January bringing April showers.

With lyrics like "All hail to the thief, but I'm not" and "Don't question my authority" there have been repeated suggestions from many musical critics that the song is based on the controversial election of George W. Bush in 2000. The band have strenuously denied this, saying in one interview, "It would be too easy for us to insult George Bush".

The song reached number 15 on the UK singles chart.

The first part of the song is in a 7/4 time signature, which switches to 4/4 about 1 minute 22 seconds in (after the words "Two and two always makes five...").

At the beginning of the song, the listener hears guitarist Jonny Greenwood plugging his guitar in, and lead vocalist Thom Yorke is heard saying "That's a nice way to start, Jonny...".