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Universal Statements and Existential Commitment

Exercise

Construct Venn diagrams to determine which of the following immediate categorical inferences are valid and which are invalid. Make sure you remember that we are not interpreting universal statements to imply existential commitment.

  1. All S are P; therefore, some S are P
  2. No S are P; therefore, some S are not P
  3. All S are P; therefore, some P are S
  4. No S are P; therefore, some P are not S