“I am just showing a spark of he persistent evil that is out there.”

In 1999, six unemployed young men were lined up against the wall at Espacio Aglutinador in Havana, like criminal suspects in a street raid, and a long horizontal line was tattooed across their backs. In exchange for their bodies, they were paid $30. The performance was repeated in 2000 in Spain with four prostitutes, who consented to have the same line tattooed for the price of a shot of heroin.

It is perhaps one of the most brutal of the infamous ‘remunerated actions’ by Spanish artist Santiago Sierra, which he has staged in countless variations and settings over the past 25 years. Others have included war veterans paid to face a corner of a gallery like scolded school kids; a young boy hired to polish the shoes of visitors during an exhibition opening; and workers tasked with shifting concrete blocks from one end of a space to another, or sitting inside cardboard boxes at a gallery for hours.

Sierra’s remunerated actions are intentionally humiliating, offensive, and arguably immoral, pushing the worlds of art and privilege face first into a nightmarish and desperate reality of the less fortunate. They pose daunting questions about our society from the vantage point of the disadvantaged, where these questions are not merely theoretical, but fundamentally existential. Exploitation is their mortar, despair is their bottom line.

While his works are unflinching and confrontational, Santiago Sierra himself remains elusive – for a long time, photographs of the artist always showed a man from behind, his face unseen. Born in 1966 in Madrid, Sierra studied fine arts in Madrid and Hamburg. But it was in Mexico, where he lived for 12 years and befriended like-minded artists like Teresa Margolles and Yoshua Okón, that he gained attention for his singular treatment of sculpture and performance as hard-hitting social and political commentary.

While Spain remains a frequent target of his biting critique, Sierra is also the country’s only contemporary artist of international acclaim, having exhibited in countless galleries, biennials, art fairs, and institutions across the world, including P.S.1 Contemporary Art Center in New York (where he paid a man to live behind a wall built into the gallery for two weeks) and Tate Modern in London. In 2003, Sierra represented Spain at the Venice Biennale, where he blocked the entrance to the Spanish Pavilion with a brick wall – only visitors with a valid Spanish passport were allowed to enter through a back door to view the exhibition, which turned out to be the remnants and detritus of the previous biennial. But Sierra has also taken his work beyond the confines of the art institution and out into the streets: parking a truck sideways across a freeway to generate a traffic jam; pasting thousands of black posters atop advertising and billboards; building a 333 metre barrier to divide the German city of Wiesbaden in two.

Not surprisingly, Sierra’s works have frequently generated not only consternation and discussion, but public outrage. Again and again, pieces have been removed or cancelled, banned from YouTube, and publicly condemned by politicians and the press. But if anything, the debates around his actions bear testimony to their relentless effectiveness. Condensing complex and charged issues of capitalism, injustice, power, racism, migration, poverty, and greed into minimal and brutal gestures, Sierra’s work maintains that rare and unpredictable capacity to shock.

One might disagree with Sierra’s political views, or be uncomfortable with the anger and harshness of his pieces. However, they certainly do not allow their audience to remain indifferent. Being confronted with Santiago Sierra’s art means being implicated – it comes with conflicting feelings, a sense of shame, and a bad conscience. It is one thing to view an exhibition about questionable circumstances elsewhere, easy to consume and forget; it is another thing entirely to have these questionable circumstances dragged into a gallery, played out before us, and dumped right at our feet.