On one of London’s streets, you come across a sentence written in large, bold letters: “If graffiti changed anything, it would be illegal.” The piece is thought to have been placed on a wall in South London around 2011.

The sentence itself is not Banksy’s invention. It is an adaptation of the line attributed to the anarchist thinker Emma Goldman: “If voting changed anything, they’d make it illegal.” Banksy shifts the subject here from voting to graffiti, and in doing so deliberately builds a layered, self contradicting irony, because graffiti is already illegal.

This self contradicting structure is exactly the kind of intellectual game Banksy loves. The piece carries both a belief in the political power of street art and a deep scepticism about that same power, at the same time.

This is one of the rare works in which Banksy relies more on language and words than on visual imagery. That makes it one of the best examples showing that the artist is not just an image maker but also a sharp player with words.