Student Material
Chapter 4: Logic – inductive force
Students’ material: solutions
A
1 Yes; 2 Yes; 3 Yes; 4 No; 5 No; 6 Yes; 7 Yes; 8 No; 9 No; 10 Yes
Note
Where these arguments are inductively forceful, when we write them in
standard form we would indicate this by writing ‘Probably’ in front of
the conclusion.
B
1 greater than; 2 less
than; 3 greater than; 4 greater than; 5 greater than; 6 can’t say; 7
greater than; 8 less than; 9 greater than; 10 can’t say
C
1 Yes; 2 Yes; 3 Yes; 4 No; 5 No; 6 No; 7 Yes; 8 No; 9 Yes; 10 No
D
1 a; 2 b; 3 c; 4 a; 5 b; 6 a; 7 b; 8 c; 9 b; 10 a
E
1 No; 2 No; 3 Yes; 4 Yes; 5 Yes; 6 No; 7 Yes; 8 Yes; 9 Yes; 10 Yes
Note
In all of the cases where the inductive
inference is forceful, we are assuming that all other factors that
could affect the predicted event/circumstance remain stable. For
instance, in the case of the pie eater in Question 7, we can reasonably
expect the inference to be reliable if we are assuming that nothing has
changed since the last time he ate that person’s homemade pie – the
ingredients are the same, the method is the same, his digestive system
is the same, and so on.
F
The solutions below are just examples of possible reconstructions. These arguments can be made both deductively valid and inductively forceful.
1.
P1) John Keys changed his mind on two important public policy issues.
P2) People who change their mind on important public policy issues cannot be trusted.
P3) People who cannot be trusted shouldn’t be prime ministers.
__________________________________________________________
C) John Keys shouldn’t be prime minister.
Deductively valid
P1) John Keys changed his mind on two important public policy issues.
P2) People who change their mind on important public policy issues probably cannot be trusted to keep election promises.
P3) People who cannot be trusted to keep election promises shouldn’t be prime ministers.
__________________________________________________________
C) (probably) John Keys shouldn’t be prime minister.
Inductively forceful
2.
P1) The vast majority of Kiwi parents are decent, loving, law abiding people who want the very best for their children.
P2) They smack their children sparingly, and as a necessary correction of bad behaviour.
P3) The anti-smacking bill will make these good parents criminals.
P4) A bill that criminalizes a large number of good parents who use smacking only when necessary should not be passed.
________________________________________________________
C) The anti-smacking bill should not be passed.
Deductively valid
3.
P1) Tiger Woods seemed like an honest, faithful and hard-working person.
P2) Tiger Woods cheated on his wife.
P3) If a man that seemed to be honest, faithful and hard-working
cheated on his wife, then no man can be trusted to be faithful.
________________________________________________________
C) No man can be trusted to be faithful.
Deductively valid
4.
P1) Some countries are developing cyberweapons.
P2) If we
invest in cyberweapons and defences against cyberattackes our country
would be less at risk from those countries that have cyberweapons.
P3) We should do anything that puts our country less at risk.
____________________________________________________
C) We should invest in cyberweapons and in defences against cyberattackes.
Deductively valid
5.
P1) Sudan is one of the most volatile countries in Africa.
P2) There is going to be a vote in southern Sudan which may see it break away from the rest of the country.
P3) In the past, when volatile countries in Africa held elections that
could result in the division of the country, they usually ended in
civil war.
_______________________________________________
C) (probably) The election in Sudan is going to end in civil war.
Notice that this argument uses an inductive inference. If the sample is representative, this argument is inductively forceful.
6.
P1) Religions are almost certainly false.
P2) Without moderate religious faith there would be no radical religious faith.
P3) Without radical religious faith there would be no terrorism.
P4) Showing people that religions are almost certainly false will eliminate moderate religious faith.
__________________________________________________
C) Showing people that religions are almost certainly false will stop terrorism.
Deductively valid
7.
P1) American Muslims are assimilated into American culture.
P2) Being assimilated into American culture prevents radicalism.
_______________________________________________________
C1) American Muslims are not radical.
P3) Only radical Muslims present a terrorist threat.
_______________________________________________
C2) American Muslims present no terrorist threat.
Deductively valid
8.
P1) Greece has an ever-growing deficit that may cause it to default on its loans.
P2) When a country has an ever-growing deficit that may cause it to
default on its loans, its credit rating should be lowered.
_______________________________________
C) Greece’s credit rating should be lowered.
Deductively valid
9.
P1) If China softens its iron grip on its people it is likely to
disintegrate into many ethnic groupings in a process that will spark
civil unrest and wars similar to what happened in the Balkans.
P2) Civil unrest and wars in China are probably a much greater evil than the lack of some civil rights.
P2) China should avoid the greater evil.
________________________________________
C) At the moment China may not be ready for all the freedoms which we enjoy in the West.
Deductively valid
Notice that this argument is deductively valid only if the phrases “softens its iron grip,” “some civil rights,” and “all the freedoms which we enjoy in the West” mean more or less the same thing.
P1) If China softens its iron grip on its people it is probably
going to disintegrate into many ethnic groupings in a process that will
spark civil unrest and wars similar to what happened in the Balkans.
P2) Civil unrest and wars in China are a much greater evil than the lack of some civil rights.
P2) China should avoid the greater evil.
________________________________________
C) (probably) At the moment China is not ready for all the freedoms which we enjoy in the West.
Inductively forceful
10.
P1) Letting people vote to choose their leaders can have the disastrous consequence of electing a dictator.
P2) Good political systems do not allow for dictators to get elected.
____________________________________________________
C) Democracies are not good political systems.
Deductively valid
P1) Letting people vote to choose their leaders can have the disastrous consequence of electing a dictator.
P2) Perfect political systems do not allow for dictators to get elected.
____________________________________________________
C) Democracies are not perfect political systems.
Deductively valid
P1) Letting people vote to choose their leaders can have the disastrous consequence of electing a dictator.
P2) It is unlikely that good political systems allow for dictators to get elected.
____________________________________________________
C) (probably) Democracies are not good political systems.
Inductively forceful
11.
P1) People who are accused of political dissidence in China normally get sentenced to three to eight years in prison.
P2) Mr. Liu is in China.
P3) Mr. Liu is accused of political dissidence.
_________________________________________
C) (probably) Mr. Liu is going to get sentenced to three to eight years in prison.
Inductively forceful
12.
P1) The relationship between Cuba and the US is warming up.
P2) When the relationship between two countries warms up, it normally doesn’t take long before sanctions are dropped.
____________________________________________
C) (probably) Soon US sanctions will be abandoned.
Inductively forceful
13.
P1) Attacks on Taliban fighters in Afghanistan using drones have been blamed for some civilian casualties.
P2) When a military measure is blamed for causing civilian casualties it should not be used.
_________________________________________________________
C) Drones should not be used to attack Taliban fighters in Afghanistan.
Deductively valid
14.
P1) Pakistan is either unwilling or unable to deal with Al Qaeda and Taliban forces within its boarders.
P2) Al Qaeda and Taliban forces in Pakistan must be dealt with.
P3) The US is the only country that is willing and able to deal with Al Qaeda and Taliban forces in Pakistan.
_____________________________________________________
C) The US should deal with Al Qaeda and Taliban forces in Pakistan.
Deductively valid
15.
P1) Iran has been building an atomic fuel enrichment plant in secret.
P2) Iran reneged on an agreement which would allow it to have nuclear
power plants but prevent it from building nuclear weapons.
P3) When a country is building an atomic fuel enrichment plant in
secret, and does not agree on measures that would allow it to have
nuclear power plants but prevent it from building nuclear weapons, it
is probably after nuclear weapons.
_________________________________________________________
C) (probably) Iran is after nuclear weapons.
Inductively forceful
P1) Iran has threatened to wipe Israel off the map.
P2) A country that threatens to wipe another country off the map should not be allowed to possess nuclear weapons.
________________________________________________
P2) Iran should not be allowed to possess nuclear weapons.
Deductively valid
16.
P1) Serious change on global warming demands concerted action by the governments of all the powerful and populous nations.
P2) Serious changes on global warming are going to have large negative economic effects.
P3) Governments are unlikely to do anything that would have large
negative effects on the economy because that could mean lose of popular
support.
P4) The only thing that would push governments to take steps that would
have large negative effects on the economy is a popular outcry.
__________________________________________________
C) (probably) Serious changes on global warming will not take place without a worldwide popular outcry.
Inductively forceful
17.
P1) The industrial nations of the first world like the US, Britain,
Japan, Germany and France have built their success and prosperity on
practices which caused enormous pollution.
P2) Now these countries want industrializing nations like China and India to curb their own pollution.
P3) This demand will be very costly to industrializing nations, and will likely slow their development.
P4) Asking industrializing nations to pay for what industrialized
nations did for free is only fair if industrialized nations are going
to help industrializing nations carry the burden of cutting pollution.
______________________________________________________
C) To be fair, the industrial nations should help industrializing nation carry the burden of cutting pollution.
Deductively valid
18.
P1) Most of the growth in greenhouse emissions in the next two decades is predicted to come from China and India.
P2) Countries that are predicted to be the source of most of the growth
in greenhouse emissions in the next two decades should not be allowed
to renege on environmental agreements.
________________________________________________________
C) China and India should not be allowed to renege on environmental agreements.
Deductively valid
19.
P1) Many small island nations and peoples will be completely destroyed by the predicted sea level rise.
P2) These nations and peoples are not responsible for the predicted rise in sea level.
P3) Those most responsible for the predicted rise in sea level are the big industrial and industrializing nations.
P4) Small island nations and peoples should be compensated for the
damages they will incur from the predicted sea level rise by those most
responsible for it.
P5) Giving small island nations and peoples choice of citizenship in
any and all the countries that are most responsible for global warming,
as well as all the money and resources they will need to immigrate and
integrate into those countries is probably the only way to compensate
them for rising sea level damages.
_________________________________________________
C) (probably) Small island nations and peoples should be given choice
of citizenship in any and all the countries that are most responsible
for global warming, as well as all the money and resources they will
need to immigrate and integrate into those countries.
Inductively forceful
20.
P1) The ethnic majority in Telangana, India, are a minority in their state, and they are discriminated against.
P2) Giving the Telangana statehood would help reduce discrimination against them.
P3) We should probably do anything that would help reduce discrimination.
________________________________________________________
C) (probably) Telangana should be made into a different state.
Inductively forceful
21.
P1) Granting Telangana statehood would cause numerous other ethnic minorities to demand statehood.
P2) Having numerous other ethnic minorities demand statehood is something India cannot afford.
P3) The problem of discrimination against Telangana can be resolved by other means.
P4) The problem of discrimination against Telangana should be resolved.
________________________________________________
C) The problem of discrimination against Telangana should be resolved by other means.
Deductively valid
22.
P1) Ms. Weinstein chose and paid a sperm donor, she chose and paid
an egg donor, and she chose and paid a surrogate mom to be a
gestational carrier and to deliver the baby.
P2) Ms. Weinstein had a contract with the surrogate mom in which the baby is agreed to belong to Ms. Weinstein.
P3) When a person chooses and pays for sperm and egg donors, and a
separate surrogate mom, and then makes a contract with the surrogate
mom stating that the baby will not belong to the surrogate mom, the
surrogate mom should not have any rights over the baby.
________________________________________________
C) The surrogate mom should not have any rights over the baby.
Deductively valid
23.
P1) I gave Spencer & Jutland exclusive publishing rights to my book before e-books existed.
P2) A contract only applies to media that were known at the time of its signing.
_________________________________________________________
C) The contract with Spencer and Jutland does not apply to e-books.
Deductively valid
24.
P1) Out of about 30,000 Islamic schools in Pakistan, only 50 are connected with known terrorists.
P2) If known Pakistani terrorists are associated with only a small
number of Islamic schools, then there is a high probability that these
schools are indoctrinating children into extremism.
____________________________________________________
C) (probably) These schools are indoctrinating children into extremism.
Inductively forceful
25.
P1) In our culture property and honour follow the male line of the family.
P2) We value the honour of the male lineage more than anything, and we trace it for many generations.
P3) If a woman commits adultery she puts the male lineage in question.
P4) If the male lineage is in question there is no way to tell if the sons deserve their honour and property.
P5) If it will not be possible for us to be confident about the rights
to property and honour of many men, our whole culture will disintegrate.
P6) The only way to prevent adultery from becoming popular is by deterring women with capital punishment.
P7) Keeping our culture from disintegrating is more important than the lives of adulterous women.
__________________________________________________
C) It is necessary to put our adulterous women to death.
Deductively valid
26.
P1) Credit cards offered by the major retailers offer big discounts and no interest repayments.
P2) These cards punish you harshly for missing a payment.
P3) Consumers should be wary of credit cards that offer attractive
conditions upfront, but could have bad consequences down the line.
_______________________________________________
C) Consumers should be wary of credit cards offered by the major retailers.
Deductively valid
27.
P1) In our celebrity obsessed global culture a huge amount of money is spent on cheap entertainment like sports and pop music.
P2) These funds could be better used in other areas of culture like
science, medicine, the prevention of hunger, intercultural
understanding, the ecology, etc.
P3) Humanity should probably not spend large amounts of money on frivolous pursuits.
________________________________________________
C) (probably) We should stop idolizing sports and pop stars and start appreciating and funding real culture.
Inductively forceful
28.
P1) Over half of Europeans believe that Islam is an intolerant religion.
P2) If over half of Europeans believe that Islam is an intolerant religion then this may be true.
______________________________________________
C1) Islam may be an intolerant religion.
P3) Before allowing religions to spread throughout Europe we should make sure they are not intolerant.
________________________________________________
C2) Before allowing Islam to spread throughout Europe we should make sure it is not intolerant.
Deductively valid
29.
P1) President Obama did not make any peace.
P2) The Nobel peace prize should be given only to peacemakers.
_________________________________________________
C) President Obama shouldn’t have been awarded the Nobel peace prise.
Deductively valid
30.
P1) Tom is socially awkward, takes things too literally, and rarely gets a joke.
P2) I have a friend that behaves similarly and he said it is because he has aspergers.
_______________________________________________________
C) Tom may have aspergers.
Deductively valid
31.
P1) The only reason the news media is granted the right to the
freedoms that it has is so that it could execute its duty to keep the
public well-informed.
P2) All too often, the news media does not take this duty seriously enough and is uninformative and misinformative.
P3) Those who enjoy a right given on the condition of carrying out a related duty should carry out that duty.
_______________________________________________________
C) News providers who consistently fail to be sufficiently informative should take their obligations more seriously.
Deductively valid