Weitz' groundbreaking publication is titled "The Role of Theory in Aesthetics." This work arguably spurred much debate within the philosophy of art and is part of a larger movement known as anti-essentialism. This movement was popular in the 1950s and is similarly defended by W.B. Gallie, W.E. Kennick and Paul Ziff. Weitz's piece, however, is arguably the most popular anti-essentialist pieces, as well as one of the most debated pieces in twentieth century aesthetics. Weitz argued against the traditional essentialist methodology and proposed using Wittgenstein's family resemblance argument as an alternate method for identifying art objects. Weitz proposed that in asking "what is art?" aestheticians were really asking the wrong question altogether. The question he believed needed to be fundamentally addressed instead was "what kind of concept is 'art'?" Weitz used this question to propel both his defense of Wittgensteinian family resemblances, as well as his defense of art as an 'open concept.' Weitz is widely considered to have renewed interest within the analytical philosophy for aesthetics, where his claims have been challenged for over fifty years, most famously by Maurice Mandelbaum in the 1965 piece "Family Resemblances and Generalizations Concerning the Arts." Weitz later developed a philosophy of criticism, in which the critic must describe, interpret, evaluate, and finally theorize about the work in question.
The Role of Theory in Aesthetics, Journal of Aesthetics and Art Criticism, vol. 15 (1956), pp. 27–35; reprinted in P. Lamarque and S. H. Olsen (eds), Aesthetics and the Philosophy of Art: The Analytic Tradition, (Oxford: Blackwell, 2004), pp. 12–18.