There are many ways to view this book. The one which most appeals to me is that of a work revolving around deception.
We see, first, a long description on a form of deception: the male courting process. The fop is a man whose whole mind is dictated by fashion and style, his love supposedly conquered by nothing more than convention; he is incapable of true love because it is only through more affectation that his love can express itself.
This same love of style is found in the conniving Miranda, but she--being the other side of the coin--knows all too well that the wanton nature of love found within these men's hearts is not only manipulable, but loveable by degree. She loves only some things, only some parts of them, and her passionate heart could never fall to a single man--could never attain to marriage--precisely because she doesn't know a real flame of impassioned love. Her position of power (and, indeed, of wit) above the dandies of her day, gives the story depth. We see what Miranda is thinking--her position, particularly, one the meaning of sensual desire--is well articulated; she isn't despised, necessarily, for loving and trying to get the man she will eventually love: the friar.
What one must see about his love, however, is first that it has some all-encompassing wrongness about it, imposed from without. When the love of his life dies, she dies because he is not there; it is because he is fled that she dies, it is because he respects her dignity (her chastity, her reputation as a married woman, her virtue) that she dies. That he doesn't fight, even if he doesn't know, about the plot against his life.
This wrongness is never converted into a blessing. Rather, it is a righteousness and virtuous power which cannot be charmed--like the charm of the fops--by Miranda, not even by his lust for her. His love of virtue--the same love which lost him his actual love--is what causes it.
It must be remembered that the deception at play from Miranda--the many voices she assumes to seduce him in her letters--all go neglected, or show only that he wants friendship with her; that she is in his prayers. When she attempts to seduce him in person--to conquer him--her seductions result in nothing more than an attempted rape (on her part) and an accusation of rape (from her) against him--for she cannot simply lack his love, and her love is 'cured' by the use of power. (And why would Behn make that such an important point? :) )
In this sense, we perceive three distinct worlds: virtue, society, and love; the love is from Miranda, it is her passion; society, from those things which convey pain upon virtue (e.g., an inability to cope with the reality of his passion for his in-law sister, precisely because she is stolen from him); and virtue from love of that which is morally just, modesty and good action.
"She
frames
an
Idea
of
him
all
gay
and
splendid,
and
looks
on
his
present
Habit
as
some
Disguise
proper
for
the
Stealths
of
Love;
some
feign'd
put‐on
Shape,
with
the
more
Security
to
approach
a
Mistress,
and
make
himself
happy;
and
that,
the
Robe
laid
by,
she
has
the
Lover
in
his
proper
Beauty,
the
same
he
wou'd
have
been
if
any
other
Habit
(though
never
so
rich)
were
put
off:
In
the
Bed,
the
silent,
gloomy
Night,
and
the
soft
Embraces
of
her
Arms,
he
loses
all
the
Friar
,
and
assumes
all
the
Prince;
and
that
awful
Reverence,
due
alone
to
his
holy
Habit,
he
exchanges
for
a
thousand
Dalliances
for
which
his
Youth
was
made;
for
Love,
for
tender
Embraces,
and
all
the
Happiness
of
Life.
"