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초록

Venn diagram is a very useful way of deciding the validity of syllogisms. Truth-tree method is a tool for testing the validity of arguments in the first-order logic. I suggest here a way of how to reduce Venn diagram to truth-tree. In so doing I introduce the so-called ‘development’ of an equation of Boolean algebra, in terms of which a more detailed information can be retrieved from propositions in a syllogism. With the help of this, we can check if there is any contradiction between the premisses and the negation of the conclusion in a syllogism. I hope that this reduction could be regarded as suggesting the widely held disparagement on the diagrammatic reasoning being not well grounded.

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