Table of Contents
- 1 Can a premise be valid or invalid?
- 2 Can a valid argument have one false premise and one true premise?
- 3 What is an example of false premise?
- 4 Can you make an invalid argument valid by adding premises?
- 5 Can a syllogism have more than two premises?
- 6 How do you know if a syllogism is valid?
- 7 Is the middle term in this syllogism distributed in the premises?
Can a premise be valid or invalid?
Valid: an argument is valid if and only if it is necessary that if all of the premises are true, then the conclusion is true; if all the premises are true, then the conclusion must be true; it is impossible that all the premises are true and the conclusion is false. If this is possible, the argument is invalid.
Can a valid argument have one false premise and one true premise?
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 invalid argument has all true premises, then the conclusion must be false.
Do premises have to be true to be valid?
It is important to stress that the premises of an argument do not have actually to be true in order for the argument to be valid. An argument is valid if the premises and conclusion are related to each other in the right way so that if the premises were true, then the conclusion would have to be true as well.
Can a syllogism be valid and false?
A valid syllogism is one in which the conclu- sion must be true when each of the two premises is true; an invalid syllogism is one in which the conclusions must be false when each of the two premises is true; a neither valid nor invalid syllogism is one in which the conclusion either can be true or can be false when …
What is an example of false premise?
A false premise is an incorrect proposition that forms the basis of an argument or syllogism. For example, consider this syllogism, which involves a false premise: If the streets are wet, it has rained recently. (premise)
Can you make an invalid argument valid by adding premises?
A valid argument will remain valid if we add further premises (true or false) in support of the conclusion. If an argument is valid, then it is an instance of a valid argument form. But the mere addition of further premises cannot make it possible for the argument form to have true premises and a false conclusion.
Can valid arguments have a false premise?
A valid argument can have false premises; and it can have a false conclusion. But if a valid argument has all true premises, then it must have a true conclusion. A sound argument is both valid and has all true premises.
What makes a premise false?
A false premise is an incorrect proposition that forms the basis of an argument or syllogism. Since the premise (proposition, or assumption) is not correct, the conclusion drawn may be in error. However, the logical validity of an argument is a function of its internal consistency, not the truth value of its premises.
Can a syllogism have more than two premises?
Sometimes the word syllogism is used to refer generally to any argument that uses deductive reasoning. Although syllogisms can have more than three parts (and use more than two premises), it’s much more common for them to have three parts (two premises and a conclusion).
How do you know if a syllogism is valid?
If a syllogism is valid, then the middle term is distributed at least once. If a syllogism is valid, then if a term is distributed in the conclusion, it must be distributed in a premise. If a syllogism is valid, it does not have two negative premises.
Can a valid syllogism have false premises and false conclusions?
A valid syllogism can have false premises or false conclusions. An argument is sound when it valid and has true premises. Validity is only part of what it takes to make an argument sound.
Does the validity of an argument depend on its premises?
The validity of an argument does not depend upon whether its premises or conclusions are true. It merely depends on the formal relations between the premises and conclusion. A valid syllogism can have false premises or false conclusions. An argument is sound when it valid and has true premises.
To be valid, a syllogism must have exactly three categorical terms, and their sense mustn’t vary over the course of the syllogism. A fallacy of equivocation occurs when a term is used in a different way within the course of an argument.
Is the middle term in this syllogism distributed in the premises?
For instance, the middle term (furry animals) in this syllogism isn’t distributed, and the argument is clearly fallacious. Rule 3: If a term is distributed in the conclusion, it must be distributed in the premises