What is ostension?
The word 'ostention' comes from the Latin 'ostendere', to show.
It was used by semiotician Umberto Eco to refer to moments in oral communication when, instead of using words, people substitute actions, such as putting a finger on your lips to indicate that someone should be quiet.
Folklorists Linda Dégh and Andrew Vázsonyi appropriated the term in their 1983 article "Does the word 'dog' bite? Ostensive Action as a Means of Legend-Telling" to refer to ways in which real-life actions are guided by legends.
For instance, legends of contaminated Halloween candy predated the finding of actual contaminants in treats by at least ten years (Dégh and Vázsonyi, 1983). Individuals who placed needles, razor blades and other dangerous objects in treats as pranks engaged in a form of ostension. The theory of ostension explains how easily certain elements can pass from legend to ritualised action.
Entire legend plots can be reduced to an allusive action. If a narrative is widely known individuals may become involved in real life activities based on all or part of that narrative. This is ostension in action; when legend alters or shapes the behavior of people. Real events patterned on an urban legend, fact mirroring fiction.
In a nutshell?
To folklorists, ostension is the real-life occurrence of events described by a legend. Legends we live.
Bill Ellis - Aliens Ghosts and Cults, legends we live. 2001.
Bill Ellis - Raising the Devil, Satanism, New Releigions and the Media. 2000.
Linda Dégh and Andrew Vázsonyi - Does the word 'dog' bite? 1983.

what's this site about?
what's ostension?

A card from Steve Jackson's 1995 Illuminati card game foreshadowing the event's of 9/11 by six years.