Deductive argument T/F Practice Questions

A valid argument must have a true conclusion.

FALSE: A valid argument must have a true conclusion only if all of the premises are true. So it is possible for a valid argument to ha ve a false conclusion as long as at least one premise is false

If an invalid argument has all true premises, then the conclusion must be false.

FALSE: It is possible for an invalid argument to have all true premises and a true conclusion. Ex: P1: All dogs are mammals. P2: All terriers are mammals.P3: All Terriers are dog.

All valid arguments have all true premises and true conclusions.

False

Every valid argument is a sound argument.

False

If an argument has a conclusion that is certainly false, then the argument must be invalid.

False

If an argument is invalid, then it must have at least one false premise.

False

If an argument is valid, then it must have at least one true premise.

False

If the premises and conclusion are all false, the argument must be invalid.

False

The following is a valid argument: Britney is a good musician. Christa is a good musician. Therefore, they will make a good musical duo.

False

The following is a valid argument: No splogs are crogs. All crogs are blonks. So, no splogs are blonks.

False

The following is a valid argument: Senator Clarke associates with known horologists. Therefore, the argument he just gave must be an invalid argument.

False

The following is an invalid argument: Jim is at least sixty. Jan is at least as old as Jim. So, Jan is at least sixty.

False

If a valid argument has a false conclusion, then at least one premise must be false.

TRUE: A valid argument cannot have all true premises and a false conclusion. So if a valid argument does have a false conclusion, it cannot have all true premises. Thus at least one premise must be false.

If an argument has all true premises and a false conclusion, then it is invalid.

TRUE: A valid argument cannot possibly have all true premises and a false conclusion. If some argument really does have all true premises and a false conclusion, then it is obviously possible for such an argument to have true premises and a false conclusion. So the argument is invalid.

A sound argument must have a true conclusion.

TRUE: If an argument is sound, then it is valid and has all true premises. Since it is valid, the argument is such that if all the premises are true, then the conclusion must be true. A sound argument really does have all true premises so it does actually follow that its conclusion must be true.

All sound arguments are valid arguments.

True

If a deductive argument is invalid, then it must also be unsound.

True

Some Deductive arguments have true premises, ant yet they are invalid.

True

Some invalid arguments have true premises and a true conclusion.

True

The following is a valid deductive argument: If it snows, then we will go sledding, just like when we were kids. It is snowing. So, certainly we will go sledding, just like when we were kids.

True

The following is an invalid argument: Jim is between fifty and sixty years old. Jan is older than Jim. So, Jan is older than sixty.

True

The following is clearly a valid deductive argument: All rock fish are orange and red. So, if we catch a rock fish, then it will surely be red and orange.

True