Use this tag for general questions about logic that are not categorizable under some more specific tag, like "mathematical logic", "informal logic", "classical logic", etc.
Logic is the study of formal systems of reasoning, especially of the deductive variety. It is one of the fundamental philosophical subdisciplines.
The traditional approach to logic, starting with Aristotle, is syllogistic logic. The introduction of mathematical methods during the late 19th century and with it the formulation of first-order logic have resulted in a complete transformation of the field. This development allowed to raise and answer questions about the foundations of mathematics. During the second part of the 20th century many philosophical logics have been introduced in order to tackle many other questions in philosophy.
Key notions of logic are formal languages, proofs and truth.
