Leśniewski is known for his pedantry and idiosyncratic notation, which make it extremely difficult to read and follow. As reading comes before understanding, this paper therefore attempts only one...

The aim of the article is to outline the historical background and the present state of the methodology of deductive systems invented by Alfred Tarski in the thirties. Key notions of Tarski's methodology are presented and discussed through, the recent development of the original concepts and ideas.