Validity

Validity

Validity is defined in the following way:

validity

   A property of deductive arguments which have the sort of logical structure which guarantees that if the premises are true, then the conclusion will be. This is a "conditional guarantee" of the truth of the conclusion, since the premises must still be true for the conclusion to follow. 

With our list of Basic Logical Forms, we have given you five examples of valid logical structures. Each of the inferences in these patterns carries the "conditional guarantee" of validity. That means that if the premises are true, then the conclusion must be true. The confusing part of the definition of validity is it's reference to a "conditional guarantee". Validity itself just refers to the formal properties of the structure of the argument. But if you have this structure and true premises, you may be assured of the truth of the conclusion.

An argument that has a valid structure and true premises is called a sound argument.

Consider the following true / false problems to test your understanding of validity:

True or False:

  1. In a valid argument, the conclusion is always true.
  2. In a valid argument, it is impossible for the premises to be true while the conclusion is false.
  3. If you have an argument with true premises and a true conclusion, it must be valid. 

[edit] Using the terms "true" and "valid"

In everyday discussion, it is common to say that someone has a "valid point" or that their argument is "true." Having a valid point normal just means that you have a point that is worthy of consideration. If you give an argument and someone says, "That's true," they probably mean that they agree with the truth of your conclusion. Now that we have a technical definition of validity which only applies to only to deductive arguments and which specifically focuses of structure, we should distinguish it from this everyday usage. It is more precise to say that truth and falsity are properties of claims and that validity is a property of logical structure in deductive argument.