Logic / Unit 3 Logic 095 worked example, 60 to 90 seconds
Identifying Mood and Figure
The idea
Identifying mood and figure means putting the syllogism into standard order, reading off its three form letters, then locating the middle term in each premise to fix which of the four figures it occupies.
In practice
First syllogism, already in order. All mammals are vertebrates. All whales are mammals. So all whales are vertebrates. The letters read A, A, A. The middle term is mammals: subject of the major premise, predicate of the minor. That is figure one, so the name is AAA-1. Second syllogism, arriving out of order. Some bidders are not licensed workers. All licensed workers are contractors. So some bidders are not contractors. The major premise is whichever one contains the predicate of the conclusion, contractors — that is the second sentence. Reorder first, then read. All licensed workers are contractors. Some bidders are not licensed workers. So some bidders are not contractors. Letters: A, O, O, middle term again subject then predicate. AOO-1.
Where people slip
The major premise is fixed by its terms, never by where it sits on the page. Reading the letters in the order the sentences happen to appear names a mood the syllogism does not have, and every later test then runs correctly on a form that was never there.
Your place on the trail
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