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 === Logically Equivalent Statements === Venn diagrams permit us to identify or remember logically equivalent statements. Such statements have exactly the same truth value (whether true or false) as the original. The Venn diagrams in Figure 18 permit us to identify which apparent equivalences are valid (identical Venn diagrams) and which are invalid (different Venn diagrams).

Superficially similar but non-equivalent statements:
Figure 18. Valid and invalid equivalent statements, and their Venn diagrams.