  On the other hand, Leśniewski’s concerns for the proprieties of quotation and use/mention, the object-language/metalanguage distinction, canons of correct definition, and his development of Mereology as the dominant formal theory of part and whole have all passed into the mainstream, and the logical expertise he helped to instil into a generation of Poles contributed in large part to making Warsaw the premier interbellum location for mathematical logic. In the entrance to the 1999 University of Warsaw Library building stand four concrete pillars and sculptures by Adam Myjak, celebrating the philosophical achievements of Poland. The figures represented are Leśniewski’s teacher Twardowski, his colleague Łukasiewicz, his student Tarski, and Leśniewski himself.