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Informal logic or non-formal logic is the study of arguments as presented in ordinary language, as contrasted with the presentations of arguments in an artificial, formal, or technical language (see formal logic). Johnson and Blair (1987) define informal logic as "a branch of logic whose task is to develop non-formal standards, criteria, procedures for the analysis, interpretation, evaluation, criticism and construction of argumentation in everyday discourse."
Opinion pieces of newspapers provide illustrative textbook examples of informal logic (Walton 1989), usually because these pieces are short and often fallacious. However, informal logic is also used to reason about events in the human and social sciences. In fact, most reasoning from known facts to unknown facts that uses natural language, even if combined with mathematical or statistical reasoning, can be regarded as an application of informal logic so long as it does not rely on additional empirical evidence.
Mathematics and the natural sciences
In mathematics the reasoning that occurs in proofs, though informal, is often regarded as a close approximation to a formal proof, that is, one which is carried out in a formal system of logic. Note that in practice, however, the separation between an informal mathematical proof and its formal idealization is so large that hardly anyone attempts to bridge that gap. This gap arises because most steps in informal proofs accumulate an enormous number of simple logical inferences, or other proof steps which are straightforward to most readers with enough mathematical experience. Moreover, many mathematical researchers regard proof as something other than a sequence of inference steps. Nevertheless, one of the goals of the Mizar project is to formalize the entire body of informal proofs of mathematics. More on [ Informal logic ]
Critical Thinking :: Skeptical Inquiry
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Cengage Advantage Books: Understanding Arguments: An Introduction to Informal Logic: Construct effective arg.. http://bit.ly/5HEuTx
mywiseshopping (mywiseshopping) Thu, 31 Dec 2009 07:45:59 -0000
Cengage Advantage Books: Understanding Arguments: An Introduction to Informal Logic: Construct effective arg.. http://bit.ly/5HEuTx
About.com - Logical Fallacies - Logical fallacies are presented with detailed explanations, multiple examples, and tips on avoiding them. Fallacies are organized by topic and alphabetically.
Meta Description: [ Fallacies are defects in an argument that cause an argument to be invalid, unsound or weak. Fallacies can be separated into two general groups: formal and informal. A formal fallacy is a defect which can be identified merely be looking at the logical structure of an argument. Informal fallacies a... ]
Informal Fallacies - Dr. Charles Ess, professor of philosophy and religion, explains and gives examples of logical fallacies.
Informal Logic - Article in the Stanford Encyclopaedia of Philosophy, by Leo Groarke.
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Logic and Fallacies - Atheism Web's guide to logic and fallacies in practical reasoning.
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PRIME: Fallacies - A short article on informal fallacies from the Platonic Realms Interactive Mathematics Encyclopedia.
Meta Description: [ Comman Fallacies Exposed, from the Platonic Realms Interactive Math Encyclopedia. ]
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Meta Description: [ Leo Kee Chye 's Personal E-zines whose main content includes writings on Critical Thinking, Philosophy, Economics and Finance. ]
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Meta Description: [ Descriptions of common fallacies. ]
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Thinking Straight - A brief introduction to informal logic and argument.
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Meta Description: [ Fallacies are defects in an argument that cause an argument to be invalid, unsound or weak. Fallacies can be separated into two general groups: formal and informal. A formal fallacy is a defect which can be identified merely be looking at the logical structure of an argument. Informal fallacies a... ]
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