Virtuality is a term used by Ted Nelson for what he considers the central issues of software design. "Virtuality" refers to the seeming of anything, as opposed to its reality. (This has been the dictionary meaning of "virtuality" since at least the 18th century). Everything has a reality and a virtuality. Nelson divides virtuality into two parts: conceptual structure and feel. In every field these have different roles. The conceptual structure of all cars are the same, but the conceptual structure of every movie is different. The reality of a car is important, but the reality of a movie is unimportant—how a shot was made is of interest only to movie buffs.