Logic

Introduction
Scope and basic concepts
Logical notation
Logical systems
Definitory and strategic inference rules
Rules of ampliative reasoning

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Related Questions

How are the logical connectives not, and, or, and if-then used in formal logic?
How can an argument have true premises and still be logically invalid?
How can inductive reasoning lead to a conclusion that is mistaken?
How did Arabic and Latin philosophers develop logic during the Middle Ages?
How did Aristotle help establish the formal study of logic?
How did Aristotle use syllogisms to study valid arguments?
How did Bertrand Russell and Alfred North Whitehead connect logic and mathematics in Principia Mathematica?
How did Boethius’s translations shape medieval European study of logic?
How did Jean Piaget use logical structures to study children’s cognitive development?
How did John Venn use diagrams to show relationships between classes?
How did Ludwig Wittgenstein use the idea of language-games to discuss meaning?
How did Philipp Melanchthon present Aristotle’s logic in his textbooks?
How did Prodicus’s study of synonyms contribute to logical analysis?
How did Zeno of Elea use reductio ad absurdum arguments?
How did ancient Greek mathematics influence early logical reasoning?
How did set theory become connected to the foundations of mathematics?
How did the Sophists contribute to the development of argumentation in ancient Greece?
How did the rise of algebra inspire the use of symbols in modern logic?
How do existential and universal quantifiers represent claims about individuals?
How do necessity and possibility extend the scope of logic?
How does a contradiction differ from a logically true proposition?
How does a forensic scientist’s reasoning about human bones illustrate inductive inference?
How does first-order logic with identity differ from first-order logic without identity?
How does logical semantics explain the truth of logical statements?
How does logical validity depend on the structure of an argument rather than its subject matter?
How does model theory connect language with possible interpretations?
How does reductio ad absurdum try to establish a claim?
How does replacing nonlogical terms with variables reveal an argument’s logical form?
How does second-order logic go beyond first-order logic?
How does the statement that somebody envies everybody imply that everybody is envied by somebody?
Why are logically true propositions true in every possible scenario?
Why did Alfred Tarski’s work on truth become important to logical semantics?
Why did Ramón Llull attempt to symbolize concepts in Ars magna?
Why did Renaissance humanists criticize medieval logic?
Why did logic and mathematics become closely linked in the modern era?
Why does the order of quantifiers matter in a logical statement?
Why is the tradition that Parmenides invented logic considered a legend?
Why must a deductively valid conclusion be true when its premises are true?

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External Websites

Rebus Community - Introduction to Philosophy: Logic - What is Logic?
Carnegie Mellon University - Department of Mathematical Sciences - Logic and Proof (PDF)
Milne Publishing - A Concise Introduction to Logic - Why study logic?
Oxford University Research Archive - Logos, logic and maximal infinity
Humanities LibreTexts - What is Logic?
ABC listen - The Philosopher's Zone - Logic: if + then = why?
National Center for Biotechnology Information - PubMed Central - Logic, Reasoning, and Verbal Behavior
The University of Hong Kong - Philosophy Department - What is logic?
Pima Open Digital Press - An Introduction to Logic - Basics of Logical Analysis Overview
Stanford Encyclopedia of Philosophy - Logic and Ontology

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logic - Student Encyclopedia (Ages 11 and up)

Gottlob Frege German philosopher of mathematics, logic, and language Gottlob Frege.

Logic

philosophy

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Jaakko J. Hintikka

Jakko Hintikka was a Professor of Philosophy at Boston University. He was known as the main architect of game-theoretical semantics and of the interrogative approach to inquiry and also as one of the architects...

Jaakko J. Hintikka

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Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....

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Last updated

Nov. 1, 2026 •History

Logic, the study of correct reasoning, especially as it involves the drawing of inferences. This article discusses the basic elements and problems of contemporary logic and provides an overview of its different fields. For treatment of the historical development of logic, see logic, history of. For detailed discussion of specific fields, see the articles applied logic, formal logic, modal logic, and logic, philosophy of. An inference is a rule-governed step from one or more propositions,...

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