Week 2
What are the five famous Argument forms
1) Modus Ponens (affirming the antecedent 2) Modus Tollens (denying the consequent) 3) Hypothetical Syllogism 4) Disjunctive Syllogism 5) Constructive Dilmma
Counterexample
1) different substitution instance of same argument 2) obviously true premises/ false conclusion
disjunction form
A or B
Constructive Dilemma
A or B If A then C If B then D therefore C or D
example of disjunction I will call or email What is A and B
A: I will call B: I will email
example of Conditionals If it rains, then the grass will grow What is A and B
A: It rain B: the grass grows
example of negation It is not raining what is A?
A: it is raining
Example of Hypothetical Syllogism If it rain, then it is wet. If is wet, then there are puddles. So, if it rain, then there are puddles
A: it rains B: it is wet C: there are puddles Structure: If A then B If B then C therefore A then C
Classify as Hypothetical Syllogism, Disjunctive Syllogism, Constructive Dilemma, or none Either the "eye for an eye" principle is interpreted literally or it is interpreted figuratively. If it is interpreted literally, then the state should torture torturers, maim maimers, and rape rapists. If the "eye for an eye" principle is interpreted figuratively, then it does not necessarily demand death for murderers. So, either the state should torture torturers, maim maimers, and rape rapists, or the "eye for an eye" principle does not necessarily demand death for murderers.
Constructive Dilemma
What is the form of the following argument? Bob is a cat or a dog. Bob is not a dog. So, Bob is a cat.
DS (Disjunctive Syllogism)
Classify as Hypothetical Syllogism, Disjunctive Syllogism, Constructive Dilemma, or none It is not true that acts are right because God approves them. But either acts are right because God approves them, or God approves of acts because they are right. Therefore, God approves of acts because they are right.
Disjunctive Syllogism
Classify as Modus Ponens, Modus Tollens, Hypothetical Syllogism, Disjunctive Syllogism, Constructive Dilemma, or none A severe depression will occur given that the economy collapses. The economy collapses if inflation soars. So, inflation soars only if a severe depression will occur.
Hypothetical Syllogism
Conditionals form
If A then B
Modus Tollens (denying the consequent)
If A then B Not B, therefore A
Hypothetical Syllogism
If A then B If B then C therefore if A then C
Modus Ponens (affirming the antecedent) MP
If A, then B. therefore B
Example of Modus Tollens If it rains, then it is wet
It is not wet so, it did not rain
example of Modus Ponens if it snows, then shovel,
It snows therefore I shovel
Please identify the form of the following argument. If none of those listed, select 'none'. Riley is a dog. If Riley is a dog, then he barks. So, Riley barks.
MP (Modus Ponens)
Classify as MP, MT, or none Souls transmigrate. But it is wrong to eat animals if souls transmigrate. Hence, it is wrong to eat animals.
MP: modus ponens
What is the form of the following argument? If A, then B. Not B. So, Not A.
MT (Modus Tollens)
Three key statements types that are always valid
Negation Disjunction Conditionals
Classify as MP, MT, or none Rilke is a dreamer if he is a poet. Therefore, Rilke is a poet.
None
Please identify the form of the following argument. If none of those listed, select 'none'. A or B. Not B. So, Not A.
None
Example of Disjunctive Syllogism
You kept the class or dropped the class. you did not keep the class So you dropped it.
valid deductive form
any argument that has this form is always going to be valid
Classify as Hypothetical Syllogism, Disjunctive Syllogism, Constructive Dilemma, or none If you want to ruin your life, you should take hard drugs. But you don't want to ruin your life. So, you should not take hard drugs.
none
Classify as Hypothetical Syllogism, Disjunctive Syllogism, Constructive Dilemma, or none The sky is blue. The sky is cobalt blue only if it is blue. Hence, the sky is cobalt blue
none
Classify as Hypothetical Syllogism, Disjunctive Syllogism, Constructive Dilemma, or none If my society approves of genetic engineering, then genetic engineering is right. But my society does not approve of genetic engineering. Hence, genetic engineering is not right.
none
Classify as Modus Ponens, Modus Tollens, Hypothetical Syllogism, Disjunctive Syllogism, Constructive Dilemma, or none Mercy killing is morally permissible only if it promotes a greater amount of happiness for everyone affected than the alternatives. And mercy killing does promote a greater amount of happiness for everyone affected than the alternatives. Therefore, mercy killing is morally permissible.
none
Classify as Modus Ponens, Modus Tollens, Hypothetical Syllogism, Disjunctive Syllogism, Constructive Dilemma, or none Philosophy is important if ideas are important. And assuming that ideas change lives, ideas are important. Hence, if philosophy is important, then ideas change lives.
none
Negation form
not a not stands for -
When is key to Modus Ponens and Modus Tollens
they have to follow exact order
Disjunctive Syllogism
two types: 1) A or B Not A, therefore B 2) A or B Not B therefore A