Today we continued talking about inference rules: modus ponens, modus tollens, simplification, conjunction, etc.
We stress the need of building valid arguments by using the given premises and application of various inference rules to get to a particular conclusion.
I was able to engage the students by showing different examples including the ones given in English sentences where the premise variable need to be chosen in order to translate to logical statements.
We had a very engaging class activity. The students were able to write the premises and the conclusion in terms of premise variables p, q, r, and s.
A few were able to build the argument step by step, applying the hypothetical syllogism to the correct premises. The hint of using contrapositive was given so they could connect the different premises.
One of the students explained the problem on the blackboard and we had interesting discussions and questions.
One of them asked me: "how do we know we have to use contrapositive and what to do?" I tried to be specific by saying that we have negations among the premises but that there is not a single recipe to build a valid argument.
Bottom line: practice, practice, practice the application of the inference rules. Homework will be posted soon! 😊
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