Douglas Adams (in 1999 no less):

[T]he reason we suddenly need such a word [as “interactivity”] is that during this century we have for the first time been dominated by non-interactive forms of entertainment: cinema, radio, recorded music and television. Before they came along all entertainment was interactive: theatre, music, sport—the performers and audience were there together, and even a respectfully silent audience exerted a powerful shaping presence on the unfolding of whatever drama they were there for. We didn’t need a special word for interactivity in the same way that we don’t (yet) need a special word for people with only one head.

As Eno pointed out, by naming something you say, “this is now real.” We can define something just as much by what is than we can by what is not. Unhappiness, for instance, teaches us invaluable lessons about happiness. When, then, will “wireless” become extinct?

[This and this via]