Branch of Philosophy


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What Is Logic?

Feelosofi  –  Logic is the study of how to think and construct arguments correctly. It involves using certain rules to reach correct conclusions based on the premises or information provided. There are two main types of logic, namely deductive logic and inductive logic.

Deductive logic is used to draw definite conclusions from given premises, while inductive logic is used to reach conclusions that are more likely based on evidence and observations, although not always necessarily true. This logic is an important tool in critical thinking, reasoning, and decision making, helping us understand and evaluate arguments and assisting us in constructing strong and convincing arguments.

Informal Logic

Informal logic in the philosophy of logic refers to the use of logical rules and concepts in everyday language, not in the form of rigid mathematical symbols as is often used in formal logic. It relates to the way we think and argue in everyday life without following the mathematical notation typical of formal logic.

The concept of informal logic involves various aspects such as inductive reasoning, analogical reasoning, authority reasoning, reasoning errors, and others. It helps us understand how we make decisions, make arguments, and identify errors in thinking. An example is when we use analogies to make conclusions, such as “If A is greater than B and B is greater than C, then A must be greater than C.” This is an example of informal logic that helps us in everyday thinking and decision making. Informal logic is highly relevant in the context of everyday life and plays an important role in understanding how we think and argue.

Formal Logic

Formal logic in the philosophy of logic is a branch of logic that uses mathematical notation, symbols, and strict rules to analyze and evaluate the structure of arguments. It focuses on the relationship between the premises and conclusion in an argument, as well as whether the argument is valid or not. Formal logic tries to eliminate elements of language and context so that it can identify correct arguments purely based on their logical structure.

Examples of formal logic include deductive reasoning, which uses rules such as modus ponens and modus tollens to produce definite conclusions from given premises. In formal logic, if the premises are true, then the conclusion must be true.

Formal logic also includes mathematical reasoning, such as propositional algebra and predicate algebra, which are used to analyze statements and arguments involving logical propositions and quantification. It makes it possible to define statements, do calculations, and evaluate the correspondence between arguments and logical provisions.

Formal logic helps us understand the basics of universal and abstract reasoning, which can be applied in various contexts. It is also used in mathematics, computer science, and logical problem solving. Thus, formal logic is an important tool in the philosophy of logic to analyze and evaluate arguments rigorously and without ambiguity.

Symbolic Logic

Symbolic logic, also known as mathematical logic, is a branch of logical philosophy that uses mathematical symbols and formal notation to analyze and evaluate arguments. In symbolic logic, natural language is replaced by mathematical symbols, such as letters, numbers, and logical operators, so that arguments can be expressed more clearly and precisely.

Examples of symbolic logic include propositional logic and predicate logic. Propositional logic involves propositions, which can be true ( True ) or false ( False ), and logical operators such as “and” ( AND ), “or” ( OR ), and “not” ( NOT ). Predicate logic further classifies propositions into subjects and predicates, using quantifiers such as “for all” (∀) and “is” (∃) to describe the relationships between various entities in statements.

Symbolic logic allows a rigorous and formal analysis of the correspondence between premises and conclusions in arguments. It is used widely in mathematics, computer science, science, and engineering to design and evaluate logical systems. Symbolic logic also helps eliminate ambiguity in natural language and allows clear comparisons between different arguments.

Mathematical Logic

Mathematical logic is an important branch of the philosophy of logic that applies mathematical principles and methods to understand and analyze logical relationships and argument structures. It uses symbolic notation and mathematical rules to evaluate the truth and suitability of arguments. Mathematical logic is closely related to concepts in mathematics, including propositional algebra, predicate algebra, and set theory.

In mathematical logic, arguments are converted into symbolic form using mathematical symbols such as propositions, variables, quantifiers, and logical operators such as “and” ( AND ), “or” ( OR ), and “not” ( NOT ). This makes it possible to rigorously evaluate arguments and ensure the correctness of conclusions based on the given premises.

One important part of mathematical logic is deductive reasoning, where the conclusions drawn are necessarily true if the premises are true. Mathematical logic also includes mathematical proof, which is the process of using logical rules to prove the truth of a mathematical statement.

Mathematical logic is a powerful tool in reasoning, mathematics, science, and engineering. It helps identify and analyze logical errors, develop mathematical theorems, and understand the basics of logical structures in various disciplines.


What is logic?

Certainly! Here are five frequently asked questions (FAQs) about logic:
What is logic? Logic is the systematic study of reasoning and the principles of valid inference. It provides a framework for evaluating and constructing arguments and identifying the relationships between statements.

What are the main branches of logic?

Logic is divided into several branches, including propositional logic (concerned with the logic of propositions or statements), predicate logic (dealing with the logic of predicates and quantifiers), modal logic (exploring necessity and possibility), and symbolic logic (using symbols to represent logical relationships).

How does logic help us in everyday life?

Logic plays a crucial role in our daily lives by helping us make sound decisions, solve problems, and assess arguments. It enables us to think critically, identify fallacies, and reach valid conclusions.

What are deductive and inductive reasoning?

Deductive reasoning involves drawing specific conclusions from general premises, with the aim of producing valid arguments. Inductive reasoning, on the other hand, infers general conclusions from specific observations, aiming to make probable arguments based on evidence.

How can we use logic to identify fallacies in arguments?

Logic provides tools for recognizing and analyzing logical fallacies, which are errors in reasoning. By understanding fallacies such as ad hominem attacks, straw man arguments, and slippery slope reasoning, individuals can assess the validity of arguments and make more informed judgments.


In conclusion, logic is a foundational discipline that underpins rational thinking, sound argumentation, and valid inference. It provides a systematic and structured approach to evaluating and constructing arguments, allowing us to distinguish between valid and invalid reasoning. The study of logic is not confined to academic philosophy; it is a practical and essential tool that permeates many aspects of our daily lives.

Through its various branches, including propositional, predicate, modal, and symbolic logic, logic offers a versatile toolkit for representing and analyzing a wide range of arguments and statements. This versatility enables us to engage in deductive reasoning, where we draw specific conclusions from general principles, as well as in inductive reasoning, where we make probable generalizations based on specific observations.

Logic also equips us with the skills to recognize and address logical fallacies, thereby enhancing our critical thinking abilities. By identifying errors in reasoning such as ad hominem attacks, false dilemmas, and hasty generalizations, we can more effectively evaluate arguments and make well-informed decisions.

In essence, logic serves as the backbone of rational thought and discourse, helping us to navigate complex problems, make informed choices, and engage in meaningful debates. It is a valuable resource for anyone seeking to sharpen their intellectual acumen and approach life’s challenges with greater clarity and precision.


  • On Knowledge” – Bertrand Russell (1910)
  • Theory of Knowledge” – J. D. Mabbott (1939)
  • Contemporary Epistemology” – Roderick Chisholm (1966)
  • The Structure of Knowledge” – Laurence BonJour (1985)
  • Epistemology: Concepts and Conceptions” – Robert Audi (1993)
  • Knowledge in a Social World” – Alvin I. Goldman (1999)
  • Epistemology: An Introduction” – Robert Audi (2016)
  • Epistemology: A Contemporary Introduction” – Robert Audi (2020)

Video Recommendations

Raymond Kelvin Nando, "Logic," Feelosofi, 31 October 2023,
Raymond Kelvin Nando
Writer, Researcher, & Philosophy Enthusiast