“Ontology is the study of what it means to be something. But knowing whether something is art belongs to epistemology—the theory of knowledge.”Arthur Danto

ARTHUR DANTO, who departed us on October 25, 2013, was the greatest philosopher of art of our time. Faced with the immense range of artistic practices that define our historical moment, it is all too easy to surrender to a pluralistic, “anything goes” approach. But Danto was able to apply his deep, encyclopedic knowledge of history and philosophy directly to the art world in unprecedented ways, and in doing so he illuminated multiple dimensions of our contemporary field.

In his final book, What Art Is (2013), Danto wrote, “The issue of what art is has become a very different matter than it has in any previous moment in history.” Today, we casually take the idea of the art world (which, it should be mentioned, Danto himself invented) for granted, but Danto reminded us that art has occupied radically different places in other cultures and epochs: Plato, for example, “drew a map of human knowledge placing art at the lowest level—with reflections, shadows, dreams, and illusions.” Plato put Greek art there because it was mimetic, as was Greek architecture, in a certain way. But Danto made this historical comparison not so much to explore Greek aesthetics as to illustrate his idea that “art is an open concept,” as he put it in his discussion of Morris Weitz’s classic 1956 essay “The Role of Theory in Aesthetics.”

The philosophical equivalent of this open-minded approach is embodied in the works of Ludwig Wittgenstein, a philosopher I have always been particularly fascinated by because of his famous excursion into architecture through his involvement in the design of his own house. When I was commissioned to design a new space for the New York University Department of Philosophy in 2004, I was inspired by Wittgenstein’s text Remarks on Colour (1977). And indeed, when Danto honored me with his critique of my project in Artforum—one of the greatest moments of my career—he closed his text with a reflection on Wittgenstein.

“Holl told me that he wanted to inscribe the two exterior door handles with some words by Merleau-Ponty and Wittgenstein, but that the NYU philosophers were unable to agree on which words. In the end the handles are eloquently, rather than merely, blank. As Wittgenstein famously said, ‘Whereof one cannot speak, thereof one must be silent.’ The central concerns of philosophy lie outside the realm of the sayable.”

Today, as the art of our time mirrors the state of our increasingly interconnected and complicated globe, Danto’s rigorous philosophical questioning is more important than ever. And so we must hope that his brilliant mind, his engaging voice, his contagious curiosity, and his profound joy in thought will continue to serve as an inspiration for future generations.

Steven Holl is an architect based in New York and Beijing.