	To be "Polish", in remote and multi-ethnic parts of the Commonwealth, was then much less an index of ethnicity than of religion and rank; it was a designation largely reserved for the landed noble class (szlachta), which included Poles, but also many members of non-Polish origin who converted to Catholicism in increasing numbers with each following generation. For the non-Polish noble such conversion meant a final step of Polonization that followed the adoption of the Polish language and culture. Poland, as the culturally most advanced part of the Commonwealth, with the royal court, the capital, the largest cities, the second-oldest university in Central Europe (after Prague), and the more liberal and democratic social institutions had proven an irresistible magnet for the non-Polish nobility in the Commonwealth. Many referred to themselves as "gente Ruthenus, natione Polonus" (Ruthenian by blood, Polish by nationality) since the 16th century onwards.