Alfred Tarski (1902–1983) was a logician. Born in Poland, he taught at the University of California at Berkeley from 1942 to 1958. He is famous for his theory of truth that appeared in “The Concept of Truth in Formalized Languages” (1933), which appeared in the Polish journal Prace Towarzystwa Naukowego Warszawskiego, Wydzial III Nauk Matematyczno-Fizycznych, and was translated into English in Logic, Semantics, Metamathematics, Papers from 1923 to 1938 (1983). According to Tarski, any theory of truth should imply the truth of “T-sentences” in natural languages. For example, “‘Snow is white’ in English is true if and only if snow is white” is a T-sentence. It is important to notice that Tarski’s theory of truth does not specify what constitutes truth but is rather about how true sentences can be defined.