2 + 2 = 5 (alternate title The Lukewarm) is the third and final single from their sixth album Hail To the Thief (2003). The song reached number 15 on the United Kingdom singles chart.The song was premiered in San Sebastian, Spain on 31 July 2002.
In 2008, the song was featured on Radiohead: The Best Of.
The song's title 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. The 'Thought Police' in the novel coerce self-aware citizens into admitting that two plus two equals five to prove the point that even though two plus two does not logically equal five, logic does not matter when no one else is willing to agree that two plus two equals anything else, under threat of pain or death.
The phrase 'hail to the thief', from which the album took its name, appears in this song. It is a reference to the song Hail to the Chief, the official anthem of the President of the United States of America. Yorke has said of the album that
“I desperately tried not to write anything political ... But it's just fucking there.”
The album title is "explicit criticism" of the 2000 election of George W. Bush over Al Gore, despite the latter receiving more of the popular vote.