Logics as bases for reasoning can be distinguished essentially by their neutral terms concerning three topics: true values, vocabulary (operators) and reasoning procedure (tautologies, syllogisms). In the Boolean logic the true values can only be 0 (false) or 1 (true). The LPI-fuzzy logic is a multi-valued logic, where degree of the truth is a fuzzy number /15/.

This way all linguistic variables (e.g. very great, very small, nearly , etc.) can be expressed by corresponding LPI /17/.

The same way classic operators, such as "and", "or", "implication", "equivalence" can be treated.

    LPI-tautologies on the LFL-base: