Intro to Logic, Class 10- Some Good Examples, Class 11- Exercises, Class 12- Constructive Use of the Syllogism
In the last lesson, we were introduced to syllogisms and the rules which must be met in order for one to be considered valid. In class 10, Prof. Casey presents examples of valid and invalid syllogisms and demonstrates how to effectively apply the rules we learned in lesson 9. Checking the validity of a given syllogism is a skill that must be practiced, which is why so much time is spent on exercises in this course.
The exercises continue in lesson 11, and we are shown that the conclusion is not always the last of the propositions presented. We sometimes have to find the conclusion elsewhere inside the syllogism. Another important takeaway from lesson 11 is that validity and truth, while related, are not the same thing. A syllogism can still be considered valid even if its premises contain false information.
Up to this point, we have been focused on determining the validity of an already present argument. In class 12, we begin to apply the same rules to partial syllogisms to see if we can construct the rest. Arguments missing either a premise or conclusion are referred to as fragmentary arguments. Of course, it is possible that no valid premise or conclusion exists for that which is missing. As in the previous two lessons, Prof. Casey uses several examples and exercises to make his points clearer.
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