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
