Standard Forms of Arguments: Videos & Practice Problems
Standard Forms of Arguments
Determine if the argument is valid and justify.
1) Students must show up to the final or they will receive a grade deduction.
2) Charlie didn’t receive the grade deduction.
∴ Charlie showed up to the final.
Valid because it takes the form of hypothetical syllogism
Invalid because the premises do not guarantee Charlie showed up to the final
Valid because it takes the form of disjunctive syllogism
Invalid because the argument commits the converse error
Determine if the argument is valid and justify.
1) If a number is divisible by 6, it is divisible by 3.
2) The number is not divisible by 3.
∴ The number is not divisible by 6.
Invalid because the argument assumes all numbers divisible by 3 are divisible by 6
Valid because it takes the form of disjunctive syllogism
Invalid because the conclusion does not follow from the premises
Valid because it uses contrapositive reasoning (modus tollens).
Identify the type of argument and come to a valid conclusion.
1) If I finish my homework, then I can go to the movies.
2) If I go to the movies, then I’ll get popcorn.
∴
Contrapositive reasoning; If I get popcorn, then I finished my homework.
Transitive reasoning (Law of Syllogism); If I finish my homework, then I’ll get popcorn
Modus ponens; If I go to the movies, then I’ll get popcorn.
Disjunctive syllogism; I finish my homework or get popcorn
Identify the type of argument and come to a valid conclusion.
1) If I forget to return the library book, I will get a late fine.
2) I forget to return the library book.
∴
Direct Reasoning (Modus ponens); I will get a late fine.
Contrapositive reasoning; I will not get a late fine.
Transitive reasoning (Law of Syllogism); If I get a late fine, I forgot the book.
Disjunctive syllogism; I return the book or get a fine.
