A version of the Aristotlian dictum: to say of what is that it is, is true; and to say of what is that it is not is false. The name ‘T schema’ was coined by Alfred Tarski (1901–1983), who formulated it as follows. Let T be the monadic predicate ‘is true’; if $\phi$ is any assertoric sentence (that is, indicative sentence without any free variables, or indexicals), $〈\phi 〉$ is a name for it; then, for all such $\phi$,

• • $T〈\phi 〉\leftrightarrow \phi$

for an appropriate conditional $\leftrightarrow$.