The study of truth and reasoning is the subject of logic, which is an interdisciplinary field. Informal logic attempts to characterize valid arguments informally, for as by naming different types of fallacies. Using formal systems such as first-order logic, formal logic represents propositions and argument patterns symbolically. Mathematical logic investigates the mathematical properties of logical systems, whereas philosophical logic applies them to philosophical issues such as the nature of meaning, knowledge, and existence. In addition to linguistics, cognitive science, and computer science, formal logic systems are used in other domains.

Aristotelian logic, stoic logic, Anviksiki, and the mohists were among the first methods of logic examined in Antiquity. The work of late-nineteenth-century mathematicians such as Gottlob Frege paved the way for modern formal logic.