But "virtuality"—the systematic approximation and representation of reality—existed long before computers. Ancient Greek philosophers used shadows to measure the universe and establish mathematical principles. Renaissance artists created a formula for vision when they applied linear perspective to art and architecture. Lenses and mirrors gave artists and scientists new imaging powers for centuries leading up to the 19th century. And photography and cinema ushered in the media age of the 20th century. The computer—"digitality"—is wholly dependent on several millennia of virtuality. The human condition is so wrapped up with virtuality, that at times it may be difficult to see that digitality is merely one small subset—a new means to that virtual end.