The counterpart to “Gilded Cage” is the even taller “Arch,” which occupies nearly the whole space underneath the marble arch in Washington Square Park. This simpler, unpainted steel cage is pierced by a mirrored opening, its form suggestive of two conjoined figures. They may appear to bystanders as weary travelers, though mega-fans of Marcel Duchamp will pick out the reference: The figures quote the French-American artist’s 1937 design for the entrance of André Breton’s Paris art gallery. Mr. Ai’s invocation of the Master in this location has a sideways political salience, if you know your downtown history. During World War I, Duchamp and his buddies broke into the Washington Square Arch and proclaimed an “independent” Greenwich Village republic, not subject to the laws and borders of the world outside.

Compared to the sphinxlike “Gilded Cage,” “Arch” wears its convictions more publicly. This is a big, public ode to freedom of movement, yoking America’s first president (a dissident) and most influential Dadaist (an immigrant). The test of a work of art’s success, though, is not how fluently it communicates a single message; the test is how forcefully it reflects, unsettles, and transforms the world in which it intercedes. By that standard, “Gilded Cage” stands as the greater achievement, enfolding inside and outside, warden and captive, into a single, synthesized public form. “Arch,” by contrast, offers less, and risks being remembered only as a selfie backdrop for woke narcissists.