The concept of the "open text" comes from Umberto Eco's collection of essays The Role of the Reader,[1] but it is also derivative of Roland Barthes's distinction between 'readerly' (lisible) and 'writerly' (scriptible) texts as set out in his 1968 essay "The Death of the Author".
[2] In this essay, Umberto Eco describes a special kind of musical works that can be organized and re-organized by the performers before they are played to the audience.
Every work of art can be read, according to Eco, in three distinct ways: the moral, the allegorical and the anagogical.
We can find an example of this in plays written by Brecht, which are "open" in the same way that an argument between two people is open: both sides (the actors and the viewers) want and anticipate a solution at the end, but no solution ever comes, leaving us to wander to find meaning.
When people believed in a geocentric world, they expected every work of art to have only one definitive interpretation, but as people found out about the universe and the magnitude of stars in the sky and their hierarchy, they began to expect more ideas to be interpreted from every work.