HOMEWORK FOR UNIT I, LESSON 5: Categorical Logic 2.0

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Assessing Categorical Arguments for Validity: Venn Diagram Edition

Directions: Use the Venn Diagramming Method to determine whether the following categorical syllogisms are valid.

  1. All philosophers are lovers of truth. No lovers of truth are close-minded people. So, no philosophers are close-minded people. 

  2. No dogs are cats, and no fish are dogs. So some cats are fish

  3. All dogs can sing, and no singers can swim. Therefore, no dogs can swim.

  4. All alcoholics need help. Therefore some sociopaths are alcoholics, since some people who need help are sociopaths.

  5. Some scavengers are fish, but some dogs aren’t fish. Therefore, some dogs aren’t scavengers.

  6. All goats are cute. All small mammals are cute. So, all small mammals are goats.

  7. Some actors are sculptors. Some poets are not actors. So, some poets are not sculptors.  

  8. All A are B. All A are C. Thus, all C are B. 

  9. Some A are not C, and all C are B. Thus, some A are not B. 

  10. Some B are C. Some B are not A. Therefore, Some A are C.