Johnston diagrams, which look similar to
Euler or
Venn diagram illustrate formal
propositional logic in a visual manner. Logically equivalent to
truth tables, they are easier to understand at a glance. By overlaying one Johnston diagram on another, deductions can be made from sets of propositions.
An interactive illustration of Johnston diagrams can be found at LogicTutorial.com (http://logictutorial.com)
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