Chapter 1.5 Flashcards
Do deductive arguments all have the same valid and invalid formats?
Yes
What is the form of a valid deductive argument?
All A are B
All C are A
therefore, All C are B
What is an argument form?
it is an arrangement of letters (A, B, C) and words ( in this case: all, none or some)such that the uniform substitution of words or phrases in the place of letters results in an argument.
What is a substitution instance?
the words or phrases in place of letters in the argument form. Any substitution instance of a valid argument form is a valid argument.
What is the form of an invalid argument?
All A are B
All C are B
Therefore, All A are C
Investigate the venn-diagram on page 60 for more clarification.
What does an invalid argument seek to prove that makes it an invalid argument?
an argument form is invalid if we can find an substitution instance having true premises and a false conclusion.
Is every substitution instance of the invalid form an invalid argument?
No. A substitution instance of an invalid form may be substitution of the valid form. for ex.
However “this situation is so rare, the book chooses to ignore them”
What is the method of counter example?
Can a counter example prove validity?
it consists of isolating the form of an argument and then constructing a substitution instance having a true premise and false conclusion. this proves the form invalid, which then proves the argument invalid.
in summary, and counter example is used to prove the form of an argument invalid. if you prove the argument form invalid you prove the argument invalid.
A counterexample can not prove validity.
What is the easiest way to interpret a counter example for categorical syllogisms?
Remember the terms cats, dogs, mammals and fish and animals and strategically substitute them into your argument form to analyze the result.
How can you analyze the non categorical syllogism deductive argument?
Consider the conditional case, replace the values with a necessary condition, such as suicide and death.
