X = X. That's obvious, right? In simplest rhetorical terms, a tautology pointlessly tells you that X is X.
Of course, the mathematical phrase "X = X" is easy to identify because it contains two of the same variable (x) and an equals sign (=). A rhetorical tautology won't look quite so obvious because it's made up of words, including synonymous words that function the same but appear different.
Here's an overview of tautology and how it compares to similar concepts such as the pleonasm and contradiction.
Tautology Definition
There are several definitions for tautology. The one relevant here is the linguistic, rhetorical definition (as opposed to the logical, mathematical definition).
A tautology is an expression of the same thing twice.
This is a broad definition, but it's also the most accurate because even in linguistic contexts people use the word tautology in many ways. Depending on how you use it, a tautology can be a rhetorical device, a figure of speech, or a stylistic error.
That said, here's one way to narrow it down. This is the most common usage of tautology in linguistics and denotes a stylistic error.
Often, a tautology describes something as itself.
You might be wondering what this looks like. A few examples should help.
Fig. 1 - Typically, you don't want to use tautologies.
Tautology Examples
There are many examples of tautology. Here's a simple one to start.
That man is a human being!
This is a tautology because men are human beings by definition.
That said, this particular tautology has its uses. It may help remind someone to treat others with respect and dignity. Another potentially useful tautology is, "It is what it is." This expression carries no denotative usefulness. However, connotatively, people know it means, "I (or you) must accept this situation."
The denotative meaning of something is its "by the book" or dictionary meaning.
The connotative meaning of something is its social or contextual meaning.
However, many tautologies are considered stylistic errors because they contain neither denotative nor connotative information.
When the situation is wide open, anything could happen.
This sentence contains no useful information. By definition, a wide-open situation means that anything could happen. Thus the redundancy in this sentence is tautological.
Proximity is essential in defining a tautology. Usually, a tautology exists in one or two sentences. The pieces of it need to connect clearly. A tautology is not saying the same thing at the beginning and end of a paragraph, for example.
In fact, some tautologies are common two-word pairings. This is one way that tautologies creep into everyday language.
Tautology Language
Most tautologies that exist in everyday language are pointless. Here are some common tautologies:
"Armed gunman"
"Free gift"
"Personal opinion"
"Necessary requirement"
How tautologies come about: Some tautologies form when people combine specific, similar phrases. Take for example, "Repeat again?" This is tautological because "repeat" already implies "do it again." This tautology probably comes from the common phrases, "Would you repeat that?" and "Come again?" The tautology "over-exaggerate" probably comes from "exaggerate" and "overstate" or "over-emphasize."
Self-Eliminating Tautologies
One other kind of tautology is the self-eliminating kind.
A self-eliminating tautology presents two alternatives that include every possible option.
That looks like this:
It will rain, or it won't.
You run to the door, or you don't.
We love each other, or we don't.
None of these phrases communicate anything overtly useful. However, self-eliminating tautologies can add emphasis to a situation. For example, one boyfriend might say to the other, "We love each other, or we don't," to draw attention to the problems in their relationship. It might represent a call to fix the relationship or call it off entirely.
Fig. 2 - Self-eliminating tautologies can say: make a choice!
Tautology vs. Pleonasm
Tautology and pleonasm are not utterly distinct. Although humans have an innate desire for clear distinctions, no one sat in a room with the brand new words "tautology" and "pleonasm" and divided them into mutually exclusive camps. Nor has any universally consistent or agreed-upon distinction been reached by linguists.
In reality, tautology and pleonasm have complex etymological histories, and their meanings overlap or differ depending on who you ask. That said, there is some sense to be made of the situation.
A pleonasm is the use of superfluous words to create redundancy in a sentence.
You can see how this definition is similar to the definition of tautology. However, the definition of pleonasm focuses on something different than the definition of tautology.
Here, the definition of pleonasm focuses on superfluous words.
On the other hand, the definition of tautology focuses on the repetition of ideas.
So although both result in a repetition of sorts, they arrive at this repetition in somewhat different ways. Here's a pleonasm:
The fiery burning in her heart could not be doused.
"Fiery burning" is technically an overuse of words, because both "fiery" and "burning" say the same thing. To prevent the pleonasm, this sentence could as easily begin with "The fire in her heart..." or "The burning in her heart..." The sentence would lose no context.
Here's a similar sentence that is better described as a tautology:
The burning in her heart was like a fire spreading.
By definition, burning is a fire spreading, so this sentence equates two identical ideas as if they were different. This sentence is aptly a tautology because the idea is redundant.
Unlike a tautology, a pleonasm often contains some useful idea; this idea is simply expressed with more words than necessary. In the above pleonasm, this new idea is that her burning heart won't go away. A tautology contains no new idea. So, while a pleonasm might contain a useless circle (fiery burning), a tautology is a useless circle.
A pleonasm is more likely to be used as a literary device (to express emphasis or perhaps clarity), whereas a tautology is more often poor style.
Tautology and Contradiction
A tautology differs more drastically from a contradiction than it does from a pleonasm.
By definition, to "solve" something, you have to understand it. There's a minuscule chance John guessed the correct answer to the math problem, but he couldn't possibly explain how he arrived at that answer — a requirement to actually solve the problem.
While some information in a contradiction might be true (maybe John doesn't understand math!), the result is incorrect. On the other hand, a tautology is not strictly incorrect; it's simply pointless.
Here's a tautology that includes similar information:
John solved a math problem using math.
This statement is redundant because, as you know, solving a math problem requires math by definition. Therefore, the above statement serves no useful purpose. It could as easily be, "John solved a math problem."
This covers the main kinds of tautology in linguistics and how to tell them apart from other concepts.
Tautology - Key Takeaways
- A tautology is an expression of the same thing twice.
- Often, a tautology describes something as itself.
- A self-eliminating tautology presents two alternatives that include every possible option.
- A pleonasm is the use of superfluous words to create redundancy in a sentence. The definition of pleonasm focuses on superfluous words, while the definition of tautology focuses on the repetition of ideas.
- A tautology differs more drastically from a contradiction than it does from a pleonasm. A contradiction expresses mutually exclusive ideas as true.
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