The liberum veto was the most notorious constitutional institution of the Polish-Lithuanian Commonwealth. Over the decades, the practice and principle of decision-making in parliament by consensus, hammered out among competing interests, hardened into the requirement of unanimity. By the second half of the seventeenth century, it became possible for a single member of parliament to curtail proceedings and nullify all laws agreed until that point.
By the mid-eighteenth century, the Commonwealth's parliament was effectively paralysed. The liberum veto has often been blamed for weakening the Commonwealth to the extent that it was unable to defend itself against neighbouring powers – who first manipulated the veto to keep the Commonwealth weak, and then partitioned the Commonwealth because the Poles had the temerity to reform their constitution, including the abolition of the veto.
It should however be remembered that given the problems with decision-making by simple majorities, the European Union makes its decisions by a mixture of unanimity and qualified majorities – not unlike the procedures in Polish-Lithuanian Commonwealth. These and other topics were debated by Professor Richard BUTTERWICK-PAWLIKOWSKI, Chairholder of the European Civilization Chair at the Natolin campus of the College of Europe and three Polish historians in the television programme "Nowe Ateny" (New Athens), broadcast on 18 January 2017.
The programme (in Polish) may be viewed here.