The Canadian actor/director Robert Lepage is a great virtualist. In the last scene of his one-man performance The Far Side of the Moon his freefall cosmonaut is always firmly grounded. He does not use wires or other hidden techniques to pretend to be in zero gravity. Instead he uses a combination of a mirror and a row of chairs tipped at an impossible angle to create the illusion of a body moving in freefall, and we as the audience are given a choice. We can either watch the performer roll around over a line of airport seating glued on its back to the stage – or we can choose instead to look only into the mirror behind it. In the reflection we see, not a middle-aged man contorting himself on the floor in some strange choreography, but a majestic human moving effortlessly in a weightlessness which seems somehow perfectly natural for him.
Perhaps it is no coincidence that this scene corresponds directly with the OED's example from 1859:
Applied to the apparent focus or image resulting from the effect of reflection or refraction upon rays of light. A familiar instance of a virtual image is that formed by a common looking-glass of an object in front of it: the image of an object under water is virtual.
Lepage does not force our eye one way or the other but allows us to make our own decisions – do we look at the reflection, or the actuality, or both? For myself, I like to try to see both simultaneously but I do wonder whether this is really possible, and that in turn leads to me wonder whether virtuality is about choice?