Logic Quiz 3

define inductive argument

An inductive argument is one where the conclusion is meant to be probably true, given the premises; where the author of the argument intends the premises to establish, with some high degree of probability, that the conclusion is true.

What logical conclusion can you draw about an argument that is valid but has a false conclusion

Any argument that is valid but has a false conclusion must have at least one false premise.

are inductive arguments truth preserving

Inductive arguments are not truth-preserving, since the conclusion of any inductive argument may be false, even though the premises are true.

is it possible for a valid argument to have true premises and false conclusion

It is impossible for a valid argument to have all true premises and a false conclusion, by definition.

Can an inductive argument guarantee truth of the conclusion if the premises are true

No, the truth of the premises of an inductive argument can never guarantee the truth of its conclusion, because inductive arguments are those where the premises are intended only to establish that the conclusion is probable.

any senator who is caught misusing campaign funds should resign his seat. Senator Greed should resign.

Senator Green was caught misusing campaign funds.

can valid argument have false premises and false conclusion

Some valid arguments have all false premises and a false conclusion. Example: All Democrats are women. Donald Trump is a Democrat. Therefore, Donald Trump is a woman. Some valid arguments have all false premises and a true conclusion. Example: All Republicans are women. Hillary Clinton is a Republican. Therefore, Hilary Clinton is a woman.

Ethel graduated from Yale. if she graduated from Yale, she probably has a superior intellect. she has a superior intellect.

Step 1: Ethel has a superior intellect. Step 2: deductively valid Step 3: n/a Step 4: n/a

good sense is of all things in the world the most equally distributed, for everybody thinks himself so abundantly provided with it, that even those most difficult to please in all other matters do not commonly desire more of it than they already possess.

Step 1: Good sense is the most equally distributed thing in the world. Step 2: not deductively valid Step 3: not inductively strong Step 4: deductive

either jack is lying or he's not. if his ears turn red he's lying. if they don't it's the truth. his eyes are red. jack is lying.

Step 1: Jack is lying. Step 2: deductively valid Step 3: n/a Step 4: n/a

people w high IQs also have psychic abilities. people w high SAT scores, which are comparable to high IQ scores, also probably have psychic abilities.

Step 1: People with high SAT scores have psychic abilities. Step 2: not deductively valid Step 3: inductively strong (maybe) Step 4: inductive

a vase was found broken on the floor; some money had been taken out of the safe, and there were strange scratches on the wall. it therefore follows that someone obviously burglarized the place.

Step 1: Some burglarized the place. Step 2: not deductively valid Step 3: inductively strong Step 4: n/a

term for strong argument w true premises

Strong arguments with all true premises are cogent arguments.

term for valid argument w true premises

Valid arguments with all true premises are sound arguments.

if you're 18 you're eligible to vote. but you're only 17. you're not eligible to vote.

invalid

Joe says that the food in the restaurant is first-rate. So it's first rate.

invalid and weak

it is unwise to touch the electrical wire. it might be hot.

invalid but strong

Social welfare is by definition a handout to people who have not worked for it. But giving people money that they have not earned through labor is not helping anyone. It follows then that social welfare does not help anyone.

valid

what guarantee does a valid deductive argument provide

A valid argument offers this guarantee: the conclusion of the argument must be true—cannot be false—given that the premises of the argument are true.

Define deductive argument

A deductive argument is one where the conclusion is meant to follow from the premises; where the author of the argument intends the premises to establish, with certainty, that the conclusion is true.

difference between an inductively strong argument vs weak

In an inductively strong argument, the conclusion is highly probable or highly likely, given the truth of the premises; in an inductively weak argument, the conclusion is only somewhat (not highly) likely, given the truth of the premises.

in what way are conclusions of deductive arguments absolute

In general, the conclusion of a deductive argument is not conclusive in any way. But the conclusion of a deductive argument that is valid is conclusive in the sense that, if the premises of the arguments is true, its conclusion must be true.

the terms valid and invalid apply to what

These terms apply only to deductive arguments.