By a trick, they are given to be real things which they resemble, as if they had existed from before. However the actualization of virtual things proceeds by differences, dispersion, and differentiation. This kind of actualization is in principle completely unrelated to identity. As a process it is no less unrelated to resemblance. Actual categories are completely different from virtual categories that these actual categories actualize.
Concepts are pure virtuality that is actualized through various modes of differentiation.
They are a multiplicity that is developed as differences. Le Corbusier's concept of architecture is exactly this type of virtual thing. This also transforms architecture into a question. According to Deleuze, questions are multiple and virtual, and they generate solutions that do not resemble their conditions. If this is the case, then the existence of virtual architecture is the existence of questions that should be answered.