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Exercise: Identifying Premises and Conclusions

Identify the premises and conclusion in the following arguments. Also determine whether the argument is valid and whether it contains hidden assumptions.

Exercises:​

1. "Since all birds have feathers and penguins are birds, penguins must have feathers."​

2. "The streets are wet, so it has rained."​

3. "If one has a good education, one gets a well-paid job. Maria has a well-paid job, so she must have a good education."​

4. "Either we raise taxes or we cut social benefits. We cannot cut social benefits. Therefore, we must raise taxes."​

5. "All politicians are corrupt. Hans is a politician. Consequently, Hans is corrupt."​

Solutions:​

  1. Premises: "All birds have feathers" and "Penguins are birds" Conclusion: "Penguins have feathers" Validity: Valid (Modus Ponens) Hidden assumptions: None essential

  2. Premise: "The streets are wet" Conclusion: "It has rained" Validity: Invalid (there are other possible causes for wet streets) Hidden assumptions: "Rain is the only possible cause for wet streets"

  3. Premises: "If one has a good education, one gets a well-paid job" and "Maria has a well-paid job" Conclusion: "Maria has a good education" Validity: Invalid (affirming the consequent fallacy) Hidden assumptions: "A good education is the only way to get a well-paid job"

  4. Premises: "Either we raise taxes or we cut social benefits" and "We cannot cut social benefits" Conclusion: "We must raise taxes" Validity: Valid (Disjunctive Syllogism) Hidden assumptions: "There are only these two options"

  5. Premises: "All politicians are corrupt" and "Hans is a politician" Conclusion: "Hans is corrupt" Validity: Valid (categorical syllogism) Hidden assumptions: The truth of the first premise is questionable