a. What is modus ponens?
b. Using the concepts of a necessary and a sufficient condition, explain: (i) Why modus ponens is valid. Give two examples. (ii) Why modus tollens is valid. Give two examples. (iii) Why denying the antecedent is not valid. Give two examples. (iv) Why affirming the consequent is not valid. Give two examples.
Look back at the arguments in the last set of s. Assess them for validity.
Look at the letters to the editor and find five letters that involve reasoning about necessary and sufficient conditions. Rewrite the reasoning into arguments involving conditionals and assess them for validity.
a. What is the difference between a necessary and a sufficient condition?
b. Give five examples of a necessary causal condition for an effect that are not sufficient conditions for it, and five examples of a sufficient causal condition for some effect that are not necessary for it.
c. Could something be a necessary part of a sufficient causal condition for some effect without being a necessary casual condition for that effect? If so, give an example.
d. Why is experimentation not a new method?