What does Jonson mean by "Comedy of Humours?"

But deeds,
and language, such as men do use; 
And persons, such as Comedy would
choose, 
When she would show an image of the times, 
And sport with
human follies, not with crimes -- 
Except, we make 'em such by loving
still 
Our popular errors, when we know they're ill. 
I mean such
errors, as you'll all confess 
By laughing at them, they deserve no
less; 
Which when you heartily do, there's hope left, then, 
You,
that have so graced monsters, may like
men.

The lines quoted above
are from the Prologue of Ben Jonson's comedy "Everyman in his Humour" (1598). In the
Prologue Jonson clearly explains his concept of the Comedy of
Humours.

1.
"an image of the
times." The Comedy of Humours deals with contemporary issues.
It is a reflection of the historical, political, and social condition of England during
the latter half of Queen Elizabeth's
England.

2. "deeds, and language,
such as men do use." It is realistic and not romantic. It does
not deal with the life of fairies but with the life of the men and women of Elizabethan
England in the language of everyday use.

3.
"sport with human follies, not with crimes." Jonson emphasizes the
satirical intent of the Comedy of Humours." The target of Jonson's satire was not some
serious crime - say for instance regicide like in Shakespeare's "Macbeth" - but human
weaknesses like greed or lust.

4.
"laughing at them, they deserve no less." The tone
of Jonson's satire was mild and light hearted, not harsh and abusive like that of Swift.
The human vices that he exposed and ridiculed were not serious crimes so they merited
only a mild rebuke in a jesting manner.

Ben Jonson's
concept of 'humour' was an extension of the medieval theory of humours which was related
to the psychological belief that the physical, mental and emotional health of a person
was controlled by the four elements namely earth, air, fire and water. If all these four
elements were in the right proportion and in harmony then a person's health was perfect.
However, if one of these four elements was in excess then that person's health was
affected and he would be classified accordingly as sanguine [air], phlegmatic [water],
choleric [fire] and melancholic [earth]. Various forms of treatment were in force during
Ben Jonson's time to set right the imbalance.

Ben Jonson
extended this theory of 'Humours' to his Comedy of Humours. According to him all human
beings suffered from some minor vice or the other - lust, self righteousness, greed etc.
So he personified these vices as characters and exhibited them on the stage so that his
audience could see these "human follies" like their own reflections in a mirror laugh at
themselves and correct themselves.