User Tools

Ambiguous middle [term]

If in a syllogism the middle term is used with two different meanings (extensions), no valid conclusion can be drawn. This is an example of a “four-term fallacy“.

For example :

Nothing light can ever be dark.
All feathers are light.
Therefore: no feather can be dark.

Description

Obviously, the term “light”, which in the above syllogism serves as the middle term that connects the two premises, is used to describe two different facts: firstly the presence of photons and secondly the absence of weight. Thus, it is an example of an equivocation, a misleading use of synonyms.

Since the identical terms do not describe the same thing, they are actually two different terms which only “coincidentally” look the same. Thus, this can be described as a variation of the four-term fallacy.

Intensional ambiguity

Also the reverse case is possible: that two terms denote the same object (e.g. both, “morning star” and “evening star” refer to the Planet Venus), but differ in their intension, which can lead to intensional fallacies (example: “The evening star can be seen in the morning.”)

More information

This website uses cookies. By using the website, you agree with storing cookies on your computer. Also, you acknowledge that you have read and understand our Privacy Policy. If you do not agree, please leave the website.

More information