Chapter 14: Categorical Syllogisms

Elements of a Categorical Syllogism (pp ) Categorical syllogisms are deductive arguments. Categorical syllogisms are composed of two premises and a conclusion. Categorical syllogisms have exactly three terms that are given the same meaning throughout the syllogism.

Elements of a Categorical Syllogism (pp ) The major term is the predicate term of the conclusion. –In a schematic of an argument form, it is represented by P. The minor term is the subject term of the conclusion. –In a schematic of an argument form, it is represented by S. The middle term is the term found in the premises but not in the conclusion. –In a schematic of an argument form, it is represented by M.

Elements of a Categorical Syllogism (pp ) The major premise contains the major term. The minor premise contains the minor term. The middle term is contained in both premises.

Standard Form Categorical Syllogisms (pp ) In a standard form categorical syllogism, each premise and the conclusion is a standard form categorical proposition. The order in which the premises and conclusion are arranged in standard form is: Major premise Minor premise Conclusion

Standard Form Categorical Syllogisms (pp ) When stating a syllogism in standard form you must find the conclusion first, since that tells which term is the major term (predicate term of the conclusion) and which term is the minor term (subject term of the conclusion).

Example: Into Standard Form You are given: Since no aardvarks are pianos, we may conclude that no Steinways are aardvarks, since all Steinways are pianos. The conclusion is: “No Steinways are aardvarks.” In standard form the argument is: Major premise: No pianos are aardvarks. Minor premise: All Steinways are pianos. Conclusion: No Steinways are aardvarks.

You’re only concerned with the form (pp ) The form is the structure of the argument The form has nothing to do with the truth or falsehood of the premises. Validity is a characteristic of the form. There are 256 distinct forms of categorical syllogisms, of which only 15 are valid.