Categorical syllogisms are the oldest form of argument to be treated in a formal, systematic way. Venn
diagrams, invented in 1880 by John Venn, are a handy way of graphically representing the formal structure of
categorical syllogisms and testing them for validity. For this discussion, create Venn diagrams for the following
arguments, indicating whether each diagram shows the argument to be valid or invalid. Hint: at least one of
them is valid and at least one is invalid.
There are some Venn diagram makers available on the Internet, or you could use PowerPoint. But Venn
diagrams are also easy to draw by hand: simply trace around a quarter (or some other round object) and fill in
the diagram using a pen or pencil. Then snap a picture of your diagrams and post it.
All hospitals are health care centers.
Some health care centers are not profit-driven institutions.
Therefore, some hospitals are not profit-driven institutions.
No tigers are herbivores.
No herbivores are malevolent.
Therefore, all tigers are malevolent.
Some disasters are catastrophes.
Some disasters are really unpleasant events.
Therefore, some catastrophes are really unpleasant events.
All venture capitalists are risk-takers.
Some risk-takers are wealthy.
Therefore, some venture capitalists are wealthy.
All Aristotelian’s are meta-physicians.
No positivists are meta-physicians.
Therefore, no positivists are Aristotelian.
Sample Solution
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