Philosophy Logic Quiz Review

This is for Duke Philosophy 101, review of Logic.

Explain what a valid argument is.

A valid argument is one where if the premises are true, the conclusion must be true. It is impossible for the premises to be true and the conclusion false.

What are the two questions one should always ask when evaluating an argument?

1. Is the argument valid or strong? 2. Are the premises true?

Is a valid argument always a good argument? Briefly explain.

No. A valid argument can still be bad if one or more of its premises are false.

What is the form of modus ponens?

If P, then Q. P. Therefore, Q.

What is the form of modus tollens?

If P, then Q. Not Q. Therefore, not P.

What is an inductive argument?

An inductive argument is one in which the premises make the conclusion probable, but do not guarantee that it is true.

Are inductive arguments valid, invalid, or sometimes one and sometimes the other?

Inductive arguments are technically invalid because their premises do not guarantee their conclusions. Instead, they are evaluated as strong or weak.

What are the two features that determine inductive strength?

Inductive strength depends on the size of the sample and how representative the sample is of the larger group.

What is an abductive argument?

An abductive argument reasons from evidence to the best explanation of that evidence. It is also called inference to the best explanation.

How do scientists try to obtain additional support for an abductive inference?

Scientists use the proposed explanation to make new predictions and then test whether those predictions are correct.

Can there be bad arguments for true conclusions? Give a super brief explanation.

Yes. A conclusion can be true even if the reasoning used to reach it is bad.

Can there be good arguments for false conclusions? Give a super brief explanation.

No. A good argument has good reasoning and true premises, so its conclusion should be true.

Explain the sense in which Gregor Mendel engaged in abductive reasoning. What would he have concluded if he had stuck to induction?

Mendel proposed hidden hereditary factors as the best explanation for the patterns he observed in pea plants. If he had relied only on induction, he would have concluded only that the observed patterns would probably continue.