A truism is a statement that is based on self-evident factual evidence that is normally obvious to the point where further proof is deemed unnecessary. A certain rhetorical or philosophical figure of speech is often designated a truism when contradicting or questioning the statement would largely be considered illogical or even foolish. This type of statement is frequently described as an intuitive or accepted truth about life in general because a large majority of people agree with it. Their agreement with a truism is usually so complete that most individuals do not question why they are in agreement with it in the first place. One of these obviously-true figures of speech sometimes appears in literature or in philosophical writing in order to emphasize a point or to create a tone of irony about the subject matter.
An aphorism is often categorized as a type of truism, although the subject matter often expresses a widely-held belief or opinion rather than an observable fact. The wording of an aphorism can sometimes be more intricate or catchy than that of other forms of truisms. It is logically possible to contradict an aphorism and to hold an opposite opinion, and people who do so tend to be a minority in many cases. The main distinction of an aphorism is that it often carries a somewhat higher degree of subjectivity than other figures of speech.
Another statement closely related to a truism is an axiom, which is a statement that is normally not examined closely beyond its surface meaning. Axioms are usually not presented with supporting evidence because this kind of proof is not considered necessary in most cases. Certain areas of logic, such as applied critical thinking sometimes involve using a particular axiom as a starting premise for a deductive argument. This use of an axiom usually does not have the same ironic purpose as is the case with a standard truism.
The study of truisms can sometimes be prone to fallacies such as presenting opinions as truths and overusing a statement to the point where its meaning becomes lost. This type of overused truism can eventually become a cliche, particularly when its subject matter illustrates a stereotype about a given idea or concept. Writers who use truisms in their literary work often put a great deal of thought into selecting one of these sayings that will remain timeless and avoid the common pitfall of turning into a cliche.