How is Ben Jonson's The Alchemist structured?

Ben Jonson prided himself on his skills of design as a
dramatist, and certainly the design of his play The Alchemist
reveals the kind of complex unity of which he was justly proud.  Samuel Taylor Coleridge
would later commend the play for having one of the three best plots in literature
(Oedipus Rex and Tom Jones having the other
two), and the skill with which Jonson manages the intricate complications of the play’s
structure is definitely impressive.  Among the most notable features of the play’s
design are the following:

• The way it begins so
  abruptly, by plunging us immediately in medias res (“into the midst
  of things”), thus demonstrating that the plot of a literary work is something quite
  different than the mere chronological order of incidents on which the plot is based. The
  plot of a play is the artistic design the playwright imposes on
  those incidents. The opening lines of the play are as startling on the page as they are
  on the stage:

readability="16">

FACE. Believe 't, I will.

SUB.
Thy worst. I fart at thee.

DOL. Have you your wits? why, gentlemen!
for love --

FACE. Sirrah, I'll strip you --

SUB.
What to do? lick figs
Out at my
–

• The
  “centripetal” nature of the play’s design, in which all the dupes are pulled into the
  house, as into a kind of vortex, where Face, Subtle, and Doll have set up their
  deceptive enterprise.


• The ways the different kinds of
  dupes represent different kinds and social levels of foolishness and greed, so that
  Jonson suggests an entire society pervaded by selfish motives (including such
  representative types as a knight, a druggist, a lawyer’s clerk, two Puritans, an
  aggressive young man whose wealth is rather recent, that youth’s attractive sister, and
  a perceptive if cynical gambler). Jonson, in other words, introduces great social
  diversity into the play; many representatives of many different social groups visit the
  house.


• The play’s adherence to the three classical
  “unities” (of time, place, action), although its unity of action has sometimes been
  disputed because some critics have seen it as being two diffuse in its presentation of
  varying incidents.  Most audiences, however (including Coleridge) have been highly
  impressed by the ways Jonson manages to tie all the threads of the plot
  together.


• The ways the characters are highly
  individualized (who can ever forget Sir Epicure Mammon?) while also representing clear
  social types.


• The methods by which Jonson complicates the
  plot in ways that at first seem threaten to unravel it, even as he
  manages to keep everything under precise control by giving his schemers opportunities to
  improvise. Thus, Dapper is being duped when Mammon unexpectedly arrives, so Dapper has
  to be quickly gotten out of the way (by being shoved into a water closet). Similar
  antics appear at the end of the play when the absent master of the house, Lovewit,
  unexpectedly appears.


• All in all Jonson manages to
  produce a play that seems both highly, comically chaotic and supremely ordered and well
  designed.