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Existential Import

When a form of logical statement that implies existence is derived from premisses in which existence is not necessarily implied, existence must first be proven.

For example:

All giant squids are deep-sea animals.
[and giant squids exist.]
There exist giant squids that are deep-sea animals.

Giant squid” refers to several species of in­verte­brates that were long thought to be merely sail­or’s yarn, i.e. some kind of mythical sea-monsters. Their ex­ist­ence has only been proven during the 20th century.

This proof of existence is re­quired in order to be able to derive an exis­tent­ial state­ment (which does require ex­ist­ence) from a uni­versal one (which does not re­quire it).

Other names

Description

A recurring issue in the validity of logical statements concerns the question of existence of the objects that the terms actually refer to. There are certain statements that are valid even if (or even because) they refer to an empty extension of a term.

For example, all universal statements (like “all A are B”) are valid even if the extension of their antecedents might be empty. In fact, if we know that it is empty, it is even guaranteed to be true ( vacuous truth). On the other side, existential statements (e.g. “some A are B”) require that the terms refer to something that actually exists (hence the name).

For this reason, the syllogism forms in which an existential conclusion is derived from one or multiple universal premisses require that the existence of certain terms is proven in order to be valid. This affects the syllogistic modi Barbari, Bamalip, Calemos, Camestros, Celaront, Cesaro, Darapti, Felapton and Fesapo.

In the example above, the existential import is made explicit by inserting a new premise. In other situation, this may be done implicitly ( enthymeme). Generally, it is to be preferred to do this explicitly, however, as this can help to avoid the so-called “existential fallacy”.

See also

About this site

Ad Hominem Info is a project to explain and categorize the most common systematic fallacies and fallacies. On this page, you will find a background article that briefly explains an important logical concept, which may be needed to better understand another article in this area.
For more information, please see the main category “logic

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