This Wednesday, painter Paula Rego died aged 87.

Documentary maker Dr Janina Ramirez said: "You changed the world through art, you fierce, fabulous female." Rego's granddaughter Grace Smart tweeted that she "was a fantastic and world-changing artist, and grandma".

Rego was often called Britain's greatest living artist. But she came from Portugal. Rego grew up under the country's Estado Novo regime. As a teenager, she was sent to an English finishing school, then spent much of her life in London.

A 2004 exhibition in PortoPortugal's second most populated city. was so popular it was open all night. In 2009 a museum of her work was established near Lisbon. And in 2010 she became a Dame Commander of the British EmpireThe second highest rank for women in the British honours system, abbreviated DBE. Men are instantly declared Knight Commander..

Rego was an uncompromising artist. She depicted women with honesty and a touch of the grotesqueThings that are strange, mysterious, sinister, ugly and disgusting, often all at once. The word descends from the Italian word for cave.. Smart wrote: "She taught me as a young woman to be absolutely and unapologetically gross."

Her works are often strange, full of cruelty. She painted and drew scenes of violence. "These are images," says writer Katherine Angel, "from which one might wake in the dark, heart-pounding".

Art critic Alastair Sooke calls her "a crusader, a battler, someone spoiling for a fight." After Portugal banned abortion in 1997, Rego produced a series of pastelsA work of art where colour is applied to a surface using a pastel stick. depicting the horrors of illegal abortions. It has been claimed these pictures convinced the public to campaign for a new referendumA direct vote by the population of a country on a particular law or issue. in 2007, which saw abortion legalised.

Some see Rego's eventual victory as proof art can change the world. They can point to other examples. Pablo Picasso's Guernica, an enormous painting depicting a Spanish Civil War bombing by Nazi Germany and Fascist Italy, woke the world up to the violence of those regimes. Norman Rockwell's The Problem We All Live With alerted Americans to the horrors of segregationA racist policy separating White and Black Americans. It was used in the southern United States from 1877 to 1968.. 

Art influences society. Contemporary artist Olafur Eliasson believes art can change the world by inspiring humans. He writes: "It can make the world felt. And this felt feeling may spur thinking, engagement, and even action."

Others disagree. People change the world. The best art does not present a clear argument but instead allows viewers to interpret it. Only a small number of people see any given painting.

And for every Picasso or Rego, there are hundreds of artists whose work did not have an impact on society.

Yes: Great art fills our minds with ideas, some of which stick around long afterwards. Those ideas may come to influence our actions at crucial moments of decision, whether we are aware of it or not.

No: The idea that art can change the world is a pleasing thought. But who can name a single moment when a painting stopped a battle, created a huge new technology or saved an endangered species? No one.

Or.... Perhaps pictures of ancient heroes inspired Napoleon to wage war, or Guernica convinced Churchill to oppose the Nazis. We will never know. The minds of others are impossible for us to access.