Door as wall. Wall as glazing. Glazing as light.
The door is an opening into an environment. Its also a bridge from one spatial condition to another.
The door is a light transference mechanism as well depending on the type of glazing and the interface between glass and solid that creates the door.
Can a door evolve from one environment to another? Can it emerge from a space to intersect with another space?
Perhaps the portal or gateway is truly the appropriate evolution of the door. From this perspective, we see where we were clearly and sense where we are going, though geometry can create a mystery if not a labyrinth ahead.
Our current time supposes a trajectory towards an absence of privacy. In effect advanced society can see everything. All our actions are exposed.
In the arms of a constructive benevolent government this is good. To the extent that government seeks to quell dissent or worse, then privacy - the closed door, or the moderated enclosure, would seem to be warranted.
Society hopes to achieve complete transparency though, as we evolve.