12.4: Review of Major Points

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Page ID: 22037

Bradley H. Dowden
California State University Sacramento

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This chapter focused on the logical forms of arguments in Aristotle's class logic. For deductive arguments involving class relationships, Venn-Euler diagramming is a useful picture method for assessing validity or invalidity. The method is applied to an argument by attempting to discover a picture of a counterexample to the argument. If one is found, the argument is deductively invalid. But if none exist, then the argument is valid.

It wasn't mentioned above, but there is a slight difference between Venn and Euler diagrams; Venn diagrams of intersecting circles always produce areas picturing every possible relationship among all the circles (which is why every circle must intersect every other circle), so they are less intuitive. Euler diagrams are more free-form and intuitive, partly because not every possibility needs to be pictured.