The "Round square copula" is a common example of the Dual Copula Strategy used in reference to the problem of nonexistent objects as well as their relation to problems in modern philosophy of language. The issue arose, most notably, between the theories of Alexius Meinong, Bertrand Russell - Gilbert Ryle playing a minor part as well in the eventual dismissal of Meinong's object theory (see Meinong's 1904 book, Theory of Objects).