1
For roughly two centuries of English theatre, a play did not begin with the play. It began with a person walking out in front of the curtain and speaking directly to the audience. The custom held from the reopening of the theatres in 1660 until the middle of the nineteenth century, and for most of that time an epilogue closed the evening in the same manner, often spoken by the actress who had died in the last act.
2
The prologue-speaker was not a character in the story that followed. He or she stood in a space that belonged to neither the stage nor the auditorium, addressed the house as itself, and said things the play could not: that the company was new, that the weather was poor, that the piece to come was a first attempt and might not please. That space was physical: an apron of stage floor projecting several feet in front of the curtain line, lit by the same candles that lit the pit, with a door opening onto it from either side. Prologues were written in rhymed couplets, ran to thirty or forty lines, and were sold at the door on an opening night for a penny. Then the speaker left, the curtain moved, and the fiction started.
3
The convention is easy to dismiss as decoration. It was doing at least three jobs.
4
The first was practical. An eighteenth-century audience did not arrive to a dimmed house and a silent room. Lighting stayed up throughout, people entered late, and a theatre before curtain-up was closer to a busy hall than to a modern auditorium. The light came from candles in hoops hung over the pit and from oil lamps along the front of the stage, neither of which could be reduced without a man on a ladder. Boxes were taken for the season and their holders arrived when they chose, while the pit filled early because its benches were unnumbered and a servant sent ahead to hold a place gave it up only when his master appeared, sometimes in the second act. Somebody had to get the room's attention, and a person speaking to it directly is a more reliable instrument for that than a scene between two characters who are pretending the room is not there.
5
The second was contractual, in a loose sense. The prologue set the terms: what kind of play this was, what the company was attempting, what indulgence it asked. A tragedy asked for silence. A new author asked for patience. The asking was not merely polite. A first play's author took the receipts of the third night, less the charges of the house, so a piece hissed down before then paid him nothing at all, and the plea in the opening lines was about money as much as manners. The prologue told the audience what response was wanted, which is information a play must otherwise convey through its opening scene, more slowly and less reliably.
6
The third is the one that interests theatre historians most. The prologue marked a boundary. By standing outside the story and then leaving, the speaker made visible the line the audience was about to cross, and crossing it was the audience's own act. Nothing pretended the fiction had always been in progress.
7
When gas and then electric lighting made it possible to darken the house, the convention became unnecessary and it disappeared quickly. A darkened auditorium does the attention-getting on its own, and it does it without a person. But it also does the third job differently, and the difference is worth noticing: the boundary is now crossed by the audience being put in the dark rather than by being addressed. The line is still marked, and it is marked to them rather than with them.
8
The change came more slowly than the technology. Gas reached the larger London houses in 1817 and made dimming possible for the first time, since a tap can be turned where a candle cannot; but for another sixty years the lights over the audience were lowered rather than put out, because managers believed that patrons unable to see one another would stop coming. Full darkness arrived with the electric installations of the 1880s and was resisted in print by correspondents who complained that they could no longer read a programme or be seen in the box they had paid for.
9
There is a claim in the literature that goes further — that the loss of direct address produced a more passive audience — and it should be treated carefully. Audience behavior changed enormously across the same period for reasons that have nothing to do with prologues: seating was fixed, tickets were numbered, eating during performances stopped. Attributing the change to a convention that disappeared alongside a dozen others is the kind of argument that is easy to make and hard to support.
10
What can be said more safely is narrower. The prologue was a tool for managing a transition, and when the technology of the theatre made a different tool available, the older one went. What the newer tool cannot do is speak. A darkened house can silence a room, and it cannot tell that room the play is a first attempt, or ask it for patience, and companies who want to say such things now have to print them in a programme that the audience reads with the lights still up.