Tautology
In logic, a tautology is a statement which is true by its own definition, and is therefore fundamentally uninformative. Logical tautologies use circular reasoning within an argument or statement.
In linguistics, a tautology is a redundancy due to superfluous qualification.
Logical tautologies
A logical tautology is a statement that is true regardless of the truth-values of its parts. For example, the statement "All crows are either black, or they are not black," is a tautology, because it is true no matter what color crows are. As a humorous example, the tautology is famously defined as "that which is tautological". (That definition is, of course, tautological.) In a more realistic example, if a biologist were to define "fit" in the phrase "survival of the fittest" as "more likely to survive", he would be forming a tautology.
The opposite of a tautology is a contradiction, which is a statement that is always false.
Example
Sometimes a logical tautology can be quite subtle. Suppose that a news analyst were to make the following statement:
- All mainstream U.S. Senators agree that the House bill is unacceptable.
This would seem to be a meaningful statement. But suppose further that he were to also reveal his opinion that "Senator K disagrees, and has therefore shown himself to be outside of the mainstream." In this case, the analyst's definition of "mainstream" requires opposition to the House bill. Therefore his original statement was a tautology.
Linguistic tautologies
A linguistic tautology is often a fault of style. It was defined by The La Brea Tar Pits" (the the tar tar pits), Manos: The Hands of Fate, or Shiba Inu Dog. They often appear in conjunction with acronyms or abbreviations, when the original meaning fades through familiarity with the acronym itself; for example, "ATM machine", "HTML language", or "LCD display". (See RAS syndrome.)
Examples
Other examples of linguistic tautologies are: "boys will be boys," "free gift," "in this day and age," "helpful assistance," "new innovation," and "business is business".
See also
