Logic
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[section started Jan 2004]
Logic is the study of inference or reasoning. When people – especially philosophers and logicians – use the term logic, they tend to have in mind “formal logic,” a fairly technical subject usually involving lots of symbols. The techniques of formal logic are important theoretically, but have little application to “real world” reasoning, argument and critical thinking. Most of the rest of this website is concerned with logic in the broad (non-formal) sense. Nevertheless, every advanced critical thinker will be familiar with formal logic.
This page selects some (formal) logic resources likely to be useful to people whose primary interest is in critical thinking. If you are interested in (formal) logic in its own right, you should consult one of the many resource sites devoted to that topic.
See also Guides, Fallacies, Textbooks
Logic by Garth Kemmerling
A small online textbook without the exercises. Covers the material you would expect to find in a good one-semester undergraduate introductory logic subject. Heavily slanted towards formal logic but has sections on topics such as analogical reasoning and causal inference. Basically sound but a bit like eating dry wheat biscuits for breakfast. [12 Jan 04]
Manual of Job-Related Thinking Skills – US Dept of Homeland Security
You may well find this useful even if you’re not applying for promotion in the Dept of Homeland Security. Much of the document consists of a fairly technical introduction to basic logic. Working through this study guide would probably be good preparation for a range of standard tests involving logical thinking, eg the LSAT. [18 Jun 03]
A Quick Introduction to Logic by Scott Lehmann
A 29 page document (pdf file) covering the basics of logic. Too succinct and technical to be much use the first time you try to learn about logic, but may be handy for someone wanting to refresh on core topics. [5 Jul 03]
Essays
Non-Aristotelian Logic in Practice, or How to be much cleverer than all your friends (so they really hate you) by Mike Alder
Probably the most entertaining introduction to Bayesian Logic you’ll ever find. This essay was published in the magazine Philosophy Now, which is well worth a visit, or even a subscription. [9 Jun 05]