Validity refers to what is consistent or acceptable.
Validity is the property of that which is valid . This adjective (valid), which comes from the Latin valĭdus , refers to what is consistent, plausible or admissible .
For example: "An excuse of this type is not valid in an area like this" , "The judge considered that the defense lawyer's request was valid" , "Red packaging is not valid in this promotion" .
Validity in logic
The concept of validity appears in different contexts. In the field of logic , the validity of an argument is the property that is evident when the conclusion is implicit in the premises. It is important to keep in mind that an argument can be deductively valid , even if its conclusion is not true.
The following argument is valid from a logical point of view but its conclusion is not necessarily true:
1. If we are not in April, then we are in May.
2. Today we are not in April.
3. Therefore, we are in May.
While the argument is deductively valid, its conclusion may not be true (it is possible that "we are not in April" and that we are not "in May" either).
Deductive reasoning can be logically valid but offer a conclusion that is not true.
disjunctive syllogism
The scheme used to determine whether an argument is valid is called a disjunctive syllogism , since it presents two options (which we can call p and q ), eliminates one and, therefore, allows us to deduce that we are facing the other. Let's look at an example below, which may be similar to the previous one, although it is not the same:
1. The document is in the right or left drawer.
2. It is not in the left drawer.
3. Therefore, it is located in the right drawer.
In a case like this, it is enough to determine the validity of the scheme to know if its arguments are also valid, and this is possible through semantics (if it is not possible for the conclusion to be false and the premises true) or syntactic ( The scheme is valid if there is a deduction of the conclusion from the premises and axioms, using only the permitted inference rules).
Validity in inductive reasoning and deductive reasoning
Logic also contemplates inductive reasoning , which consists of studying the evidence that gives rise to the estimation of the probability of a series of arguments, in the same way as the rules for the construction of strong inductive arguments.
This differs from deductive reasoning , described in previous paragraphs, in that it is not possible to determine whether an argument is valid; For this reason, when we are faced with an induction, we must evaluate its strength, that is, the degree of probability of obtaining a true conclusion if the premises are also true.
The concept in science and at the legal level
In the field of epistemology , knowledge is valid when a certain scientific community recognizes it as true and coherent. If a person who defines himself as a ufologist maintains that the Earth was created by Martians, it is likely that the scientific community will not consider this "knowledge" to be true and, therefore, the claim will lack validity.
Of course, the validity of a theory or an unprecedented statement cannot always be evaluated in a short time, but usually many tests and verifications are necessary, some of which depend heavily on events that are difficult or impossible to reproduce by force. .
History has shown us that science can make mistakes , since it is not absolute but evolves along with the rest of human knowledge. For this reason, something that is considered invalid today may become an irrefutable truth in a few years, as has happened on many occasions.
At a legal level, finally, the validity of a norm depends on its satisfaction of the material and formal requirements .