One major topic of the play is the limited knowledge we can have of history. The accounts we make of history are comparable to the mathematical and scientific theories that Thomasina and Valentine work with: they attempt to account for what happens in the world based on the evidence we have, but there are often key missing pieces and "noise." Juxtaposing the two time periods shows that Bernard's and Hannah's theories about history are missing some major facts, and that they are making some very wrong assumptions! It also shows how human nature does not really change, even if cultural standards and philosophical or artistic movements do. The overlap of Augustus/Gus in the two time periods highlights the continuity of human nature.

As you read the play, or see it performed the purpose of the juxtaposition is to compare the two time periods.  Stoppard uses this style of writing so the reader will know things about the past that the characters in the present don't know. "When contemporary scenes are juxtaposed on the scenes of the past, the guessing-game nature of historical studies is highlighted. The audience gets to watch Bernard and Hannah try to piece together the clues, repeatedly coming up with the wrong answers. From this, they can assume that history is often put together through such lucky (and unlucky) guesses, and that at best it is, like Thomasina's formula for chaos, only a theory."