Deductive and Inductive arguments
True or False? Some inductive arguments are valid
False
Modus ponens
If p then Q P is true therefore, Q must be true
Valid does not mean
True; it does not mean the premises or the conclusion are true
3. Valid or invalid. If Elaine places her order incorrectly, the Soup Nazi won't serve her. If he refuses to serve her, she won't bring home any mulligatawny soup. Therefore, Necessarily, if Elaine places her order incorrectly, she won't bring home any mulligatawny soup.
Valid because A) Incorrect order= not being served B) Not being served = no soup took home. C) Incorrect order = no soup took home It is a chain event if 1 happens 2 will happen if 2 happens 3 will happen. If you look at this pattern 1 will eventually cause number 3 to happen
13. Valid or invalid? Every member of Tacoma's legendary little bill and the bluenotes has been elected to the Northwest blues hall of fame. Dick curtis is a member of little bills group. therefore, dick curtis must have been elected to the northwest blues hall of fame.
Valid; A) every member of this group has been elected B) Dick is a member of this group C)Since dick is part of the "every member" it means he has been elected
An argument can have false premises and false conclusion but still be
valid
In a valid deductive argument (2)
-If at least one premise is true, the conclusion must be true -if the premises are all true, then the conclusion is very probably true but not certain -If the premises are all false, then the conclusion must be false -the premises must all be true
When doing valid or invalid
-read entire sentence -find the premises and conclusion -Is it a safe conclusion to make from the premises? -if it is a safe/secure conclusion it is valid -if it is a unsafe conclusion it is invalid
A sound deductive argument has these two properties
1. It is deductively valid 2. its premises are all true
The following two ways to effectively criticize a deductive argument:
1. State an argument against of the the arguments premises 2. Argue that the conclusion is not well supported by the premises
The combination you will never find in a weak inductive argument is
Any combination is possible . T/F premises and T/F conclusion.
The only combination that you will never find in a strong inductive argument is
Any combination is possible. T/F premises and T/F conclusion.
True or False? Affirming the consequent is a valid form of reasoning.
False
True or False? All arguments with true conclusions are valid.
False
True or False? All valid arguments are sound arguments.
False
True or False? An argument with a false conclusion cannot possibly be a valid argument.
False
True or False? Denying the antecedent is a valid form of reasoning.
False
True or False? If a deductive argument is valid, then it has at least one true premise
False
True or False? If an argument is strong, then it must have a true conclusion
False
True or False? If an argument is strong, then its conclusion is likely true.
False
True or False? If an argument is weak, then it must have at least one false premises
False
True or False? If an argument is weak, then its conclusion cannot be true.
False
True or False? If an inductive argument has premises that are probably false, then the argument is weak
False
True or False? If the premises of a deductive argument are all true and the conclusion is true, then the argument must be valid.
False
True or False? If the premises of an inductive argument are all false, and the conclusion is false, then the argument is inductively weak.
False
True or False? If the premises of an inductive argument are all true, and the conclusion is true, then the argument is inductively strong?
False
True or False? If the premises of an inductive argument are all true, then the argument is cogent.
False
True or False? Modus tollens is an invalid form of reasoning.
False
True or False? Some sound arguments have false premises
False
True or False? if an argument has premises that are probably true, then the argument must be inductive?
False
True or False? some sound arguments are invalid
False
Invalid does not mean
False; NOT saying that is has false premises and/or conclusion.
Identify the argument as modus ponens, modus tollens, disjunctive syllogism, or hypothetical syllogism, none of the above 1. If Amber jogs today, then Barbara jogs today 2. If Barbara jogs today, then Ned jogs today. 3. Therefore, if Amber jogs today, then Ned jogs today
Hypothetical
when we say something is valid we are saying that
IF its premises are true, then its conclusion MUST be true
to say that an arguments is deductively valid is to say only that
If its premises are true, then its conclusions must be true
Modus tollens
If p then q q is false Therefore, p is certainly false
In a valid deductive argument
If the premises are all true, then the conclusion cannot possibly be false
16. Valid or invalid. Every member of the Seattle rock band The Daily Flash is a terrific musician. Steve Lawlor is a terrific musician. Therefore, Steve Lawlor must be a member of the Daily Flash
Invalid; A) Every member of TDF is a good musician B) Steve Lawlor is a good musician C) It never said that steve Lawlor was a member of TDF D) from your own personal knowledge you know that there are several millions of good musicians in the world who are in different bands not just TDF
11. Valid or invalid? Figure A has four equal sides. Therefore, figure A must be a square
Invalid; Because it stated 1) figure A = four equal sides 2) It never said that is was a square just that it had four equal sides. 3) A rhombus also has four equal sides
14. Valid or Invalid? Every member of little bill and the bluenotes has been elected to the Northwest Blues hall of fame. Legendary guitarist billy stapleton has been elected to the northwest blues hall of fame. Therefore, Billy must be a member of Little bills group.
Invalid; Statement says A)every member of "blue notes" has been elected B)billy has been elected C) it never said billy was in "blue notes" D) it also never said only people from "blue notes" can be elected E)other people/musicians outside of "blue notes" can be elected.
1. Valid or invalid? Since some Honda's are purple and some Honda's are trucks, it necessarily follows that Honda makes at least some purple trucks.
Invalid; It is invalid because the statements says A) Some Honda vehicles are purple B) Some Honda vehicles are trucks -It never said C) some Honda vehicles are purple trucks. If on a or b it said "all" instead of "some" this would be a valid statement
The combination you will never find in a cogent inductive argument is? a.T prem and F conc b. T prem and T conc c. F prem and F conc d. F prem and t conc e. None of the above?
None of the above
The combination you will not find in an invalid deductive argument is?
None of the above, for any combination is possible in an invalid argument
disjunctive syllogism
P or q It is false that p ( p is false ) Therefore, certainly q
In each case, does the argument seem to be strong or weak? Explain your reasoning. 4. Ed is walking the twelve miles to downtown. He just left five minutes ago. He walks at an ordinary pace. Therefore, probably he has not arrived yet.
Strong A) Ed is walking B) he is going downtown C) Downtown is 12 miles (19km) away D) He is walking at a normal rate, not fast not slow E ) he left five minutes ago F ) Conclusion is strong because at a normal walking rate nobody can travel 12 miles in five minutes.
In each case, does the argument seem to be strong or weak? Explain your reasoning. 5. Few cats are orange colored. I hear a cat meowing across the street. The cat meowing is probably not orange.
Strong A) Only a few ( very small amount ) of all cats alive in the world are orange. B) Person in statement hears a cat C) He is correct in assuming that the cat is probably not orange because if you take the total population of all cats in the world most of them (>90%) are black/gray/white/ etc. D) he said very likely not must be. If he said the cat he hears cannot be orange it would be a false/weak statement.
In each case, does the argument seem to be strong or weak? Explain your reasoning. 1. The bank robber accidentally left behind his checkbook. He also dropped his wallet that contained his drivers license. Both items were traced to Joe Doakes, who was trying to hide $10,000 in his coat when the police arrived. The bank robber escaped with $10,000 but was also covered with red dye when the dye pack exploded. Joe Doakes was found to be covered with red dye. The obvious conclusion is that Joe robbed the bank.
Strong A) Someone robbed a bank B) Only two options was that Joe robbed the bank or someone else robbed the bank C) Joe or someone else D) Statement tells us that the robber stole $10000, left his checkbook, left his wallet with Identification, and was covered in red dye E) ID and checkbook traced back to joe F) Joe had $10000 on him (which he was trying to hide) when police went to his house G) Joe was also covered in red dye H) All this overwhelming evidence clearly shows that Joe is the robber since he had the 1. same amount of money on him that was stolen 2. ID/checkbook traced back to him 3. had red dye on his body
The combination you will not find in a sound deductive argument is?
T premise & a F conclusion T premises & invalid reasoning F premises & valid reasoning F premises & true conclusion
2.valid or invalid? No cat is a reptile. No reptile is a Splurp. So, no cat is a splurp
This is invalid; It is invalid because it states A) Cat ≠ Splurp B) Reptile ≠ Splurp It never said C) cat ≠ Splurp.
True or False? A deductive argument can have false premises and false conclusion and yet be valid
True
True or False? An argument can be invalid and yet have a true conclusion
True
True or False? Disjunctive syllogism is a valid form of deductive reasoning.
True
True or False? Hypothetical syllogism is a valid form of deductive reasoning
True
True or False? If a deductive argument has a false premise, then it is not a sound argument.
True
True or False? Modus ponens is all form and no content.
True
True or False? Some invalid arguments have true premises.
True
True or False? Some strong inductive arguments have false premises and a false conclusion
True
True or False? Some weak inductive arguments have a true premises and a true conclusion
True
The only combination that you will not find in a valid deductive argument is?
True premises and a false conclusion
5. Valid or invalid? Father Flanagan's boys town is located in Nebraska. Nebraska is located in the United States. So, boys town must be located in the United States.
Valid A) FFBT is inside of Nebraska B) Nebraska is in the USA C) FFBT is inside of USA another way to look at this pattern is A) Ricky is wearing his shirt B) Ricky is inside the mall C) Ricky's shirt is inside the mall.
17. Valid or invalid? All the members of the ohio southpay club are left- handed. joe is a member of the ohio southpaw club. so, joe must be left handed.
Valid A) every member of this group is a lefty B) Joe is in this group C) since Joe is part of "every member" it means that he is also a lefty.
4. valid or invalid? The United States House of Representatives has more members than there are calendar days in a leap year. Therefore, at least two members of the house must have the same birthday.
Valid;A) days in a leap year = 366 B) people in house of representatives > 366 C) for the sake of argument lets say there are 367 people in the house of representatives D) Since there are less days in a calendar(366) then people (367) it means that at least 2 of those 367 people have to share a birthday.
In each case, does the argument seem to be strong or weak? Explain your reasoning. 2. Exercising daily helps prevent heart attacks. Don exercises daily. Therefore, Don will probably never suffer a heart attack.
Weak A) Statement says exercising daily HELPS prevent heart attacks. B) Statement never says exercising daily completely gets rid of heart attacks. C) Even if he exercises daily other things could give him a heart attack D) What else could give him a heart attack? Family history of a weak heart, Unhealthy diet, drug overdose, a surgery gone wrong etc. E) From your own knowledge you know that even if you exercise daily your body is still at risk for several things.
In each case, does the argument seem to be strong or weak? Explain your reasoning. 3. It was sunny in Seattle yesterday for the first time in four weeks. Therefore, it will probably be sunny in Seattle all next week.
Weak A)everyday for the past month it has rained every single day (not sunny) with one exception B) only yesterday it did not rain in the entire month C) Based on the history of the entire previous month, it is foolish to think that for every day for the rest of the week it is going to be completely sunny with no rain.
Identify the argument as modus ponens, modus tollens, disjunctive syllogism, or hypothetical syllogism, none of the above 1. amber jogs today, or barbara jogs today 2. it is not the case that amber jogs today. 3. therefore, barbara jogs today.
disjunctive
True or False? If the premises of a deductive argument are all false and the conclusion is false, then the argument must be invalid.
false
Some valid arguments have true premises, and some
have false premises
valid argument:
if its premises all are true, then its conclusion MUST be true
Hypothetical syllogism
if p then q if q then R Therefore if p then r
In the case of a strong inductive argument
if the premises are all true, then the conclusion probably is true
if premises of inductive are all true, and conclusion is true the argument is
inductively strong
If a deductive argument is not valid, then it is
invalid
Some arguments can be ____ even though its premises are true and its conclusions are true
invalid
sometimes an argument is _____ even though premises/conclusions are true
invalid
Reason
is a tool of thought. We use any tool more effectively when we understand its nature and how it works.
Deductive argument (p.251)
is advanced with the aim of proving its conclusion with complete certainty, in such a way that its conclusion MUST be true if its premises are all true
Identify the argument as modus ponens, modus tollens, disjunctive syllogism, or hypothetical syllogism, none of the above 1. if amber jogs today, then barbara jogs today 2. amber jogs today. 3. therefore, barbara jogs today.
modus ponens
Identify the argument as modus ponens, modus tollens, disjunctive syllogism, or hypothetical syllogism, none of the above. 1. if amber goes jogging, then barbara goes jogging with her. 2. if is not the case that barbara will jog with amber 3. therefore, it is not the case that amber will jog.
modus tollens
to be valid does an argument need to have true premises and conclusions?
no
Identify the argument as modus ponens, modus tollens, disjunctive syllogism, or hypothetical syllogism, none of the above 1. Amber jogs today, or Barbara jogs today 2. It is not the case that Sue jogs today 3. Therefore, it is not the case that Ed jogs today.
none
Identify the argument as modus ponens, modus tollens, disjunctive syllogism, or hypothetical syllogism, none of the above 1. Amber jogs today, or Barbara jogs today. 2. It is not the case that Debbie jogs today. 3. Therefore, Barbara jogs today
none
Identify the argument as modus ponens, modus tollens, disjunctive syllogism, or hypothetical syllogism, none of the above 1. If Amber works today, then Barbara works today 2. Barbara works today 3. Therefore, Amber works today
none
Identify the argument as modus ponens, modus tollens, disjunctive syllogism, or hypothetical syllogism, none of the above 1. If Amber works today, then Barbara works today. 2. Barbara does not work today. 3. Therefore, Amber does work today.
none
Identify the argument as modus ponens, modus tollens, disjunctive syllogism, or hypothetical syllogism, none of the above 1. amber works today or barbara works today. 2. it is not the case that amber works today 3. therefore, it is not the case that barbara works today
none
Identify the argument as modus ponens, modus tollens, disjunctive syllogism, or hypothetical syllogism, none of the above 1. if amber jogs today, then barbara jogs today. 2. if is not the case that amber jogs today 3. therefore, it is not the case that Barbara jogs today
none
invalid doesn't mean
premises and conclusions are false
Invalid deductive argument
premises or conclusion are false. Maybe both
Inductive argument (p.251)
shows that its conclusion is probably or likely true, not certainly true, if its premises are all true.
True or False? Some deductive arguments are invalid, and yet they have a true conclusion.
true
True or False? Some deductive arguments have true premises, and yet they are invalid.
true
valid deductive argument does not mean
true conclusion
An argument does not need to have true premises to qualify as
valid
it is not required that an argument actually have true premises and a true conclusion to be
valid
