LessonsThe Second Figure: Conditions of Validity and Four Productive MoodsQuiz

Compare two arguments:
Case 1: All students are humans; no stone is human; therefore no student is a stone.
Case 2: Some students are humans; no stone is human; therefore some students are not stones.

The major remains universal negative, but the minor changes from universal to particular. The first includes all students under the middle; the second asserts this only of some.

The second argument cannot be strengthened to a universal conclusion on the strength of these premises alone, even if additional facts might establish one.

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Changing quantity changes the conclusion

The Second Figure: Conditions of Validity and Four Productive Moods

Compare two arguments:
Case 1: All students are humans; no stone is human; therefore no student is a stone.
Case 2: Some students are humans; no stone is human; therefore some students are not stones.

The major remains universal negative, but the minor changes from universal to particular. The first includes all students under the middle; the second asserts this only of some.

The second argument cannot be strengthened to a universal conclusion on the strength of these premises alone, even if additional facts might establish one.