When students at Universität der Künste Berlin (UdK) asked newly-minted visiting professor Ai Weiwei the definition of “art,” the dissident Chinese artist had a difficult time rising to the challenge.

“I am unable to say anything about this,” Ai told the crowd at an event introducing him to the college, according to Deutsche Welle.

After pausing to reflect (and to allow the applause to die down), he offered the following words of wisdom: “It’s a bit like with sex. One can have a lot of experience, and nevertheless find it extremely difficult to define.”

Ai Weiwei announced the return of his passport to his 111,000 Instagram followers.
Photo: Ai Weiwei (@aiww) via Instagram

Ai traveled to Berlin in late July, shortly after the Chinese government returned his passport. He had been prevented from to leave his native country since being imprisoned on charges of tax evasion for 81 days in 2011.

There had been widespread international efforts to convince China to return Ai’s passport, included a special print created by Shepard Fairey. The artist’s selfie of himself with his newly-returned passport on Instagram inspired a brief meme of imitators recreating the pose in solidarity.

Once complications with his visa application were cleared up, Ai has also traveled to the UK to attend the opening of his first major solo show in the country, at London’s Royal Academy of Arts, and then returned to Berlin. He’s now on a three-year contract with the German institution.

At UdK, roughly 100 students applied for just 16 slots in Ai’s first class, according to Deutsche Welle. When asked if politics would be on the agenda in his art course, Ai demurred: “I do not intend to put my students under pressure with them. Everyone has the right to decide for themselves on their principles.”