Introduction to Logic

Logic is the study of how to reason well, how to correctly draw inferences from our starting premises. Though logic is employed nearly everywhere, including politics, advertising, media, work, and everyday life, many people do not understand how logical reasoning works and frequently make mistakes in such reasoning. This section will help you to understand logic better and help to increase your skills in constructing and evaluating arguments.

Introductory logic



Soundness and validity

Logic and truth

Logical connectives

Rules of inference

Formal Logical Fallacies

Affirming a disjunct

Affirming a consequent

Denying the antecedent

Existential fallacy

Informal Logical Fallacies

Introduction to informal logical fallacies

False dichotomy


Ecological fallacy

Continuum fallacy

Shifting the goalposts

Naturalistic fallacy

Nirvana fallacy

Circular reasoning

Strawman arguments

Argument from ignorance

Fallacy of composition

Slippery slope fallacy

Appeals to authority

Red herrings

Cognitive biases

Additional Resources

Logic & Fallacies: a readable introductory article covering the basics of logical reasoning and logical fallacies

The Nikor Project: an excellent resource for logical fallacies

Logical Fallacies: comprehensive catalogue of brief introductions to many logical fallacies

Logically Fallacious: one of the best internet resources for logical fallacies

The Logical Place: a concise and clear discussion of many common fallacies, along with relevant examples

Fallacy Files: a collection of materials related to logical fallacies, including definitions and real world examples

Changing Minds: a useful website with materials related to rationality and critical thinking, also with considerable coverage of logical fallacies

Wikipedia List of Logical Fallacies: a very comprehensive list and an indispensable resource

Introduction to Logic: useful course materials for a university subject covering logic and reasoning

Toolkit for Thinking: contains an interesting visual catagorisation of logical fallacies along with more information about each

Philosophy Pages Logic: though somewhat hard to navigate, this site contains much useful material covering the more advanced philosophical aspects of logic and reasoning

Introduction to Logic: course materials from Oxford covering a course in formal logic (advanced)

Introduction to Logic: online materials relating to formal logic and construction of proofs (advanced)