Two distinct character traditions are followed in this play.  The first, from classical Roman comedy (Plautus and Terence) is represented in the major characters who drive the plot.  These are the Senex (an old man, head of a household, representing tradition and order), the young upstart, disobedient and pleasure-seeking, and the wily servant who acts as a messenger and intervener seeking to please both and to keep them from conflict.  In Jonson’s play, these characters are Knowell Senior, Knowell the son, and Brainworm, the servant.  During the plot they pretty much keep their traditional roles, the father fretting that the son is leading a dissolute life in London where he is a student, and the servant, supposedly keeping an eye on Knowell, although actually aiding and abetting his excesses.  The second group of characters, each assigned a “humourous” personality according to the medieval division of personalities represented by the fluids of the body, are agents in the mischief; they are

Sanguine (amorous, happy, generous, optimistic, irresponsible)

Choleric (violent, vengeful, short-tempered, ambitious)

Phlegmatic (sluggish, pallid, cowardly)

Melancholic (introspective, sentimental, gluttonous)

 The theatre-goer or the reader assigns these four “humours” to character personalities in Jonson’s play:  Mr. Stephen,  Downright,  Well-bred, Justice Clement, Kitely, etc. As the play moves forward and as each character is introduced, the Elizabethan audience, who knew these conventions well, recognizes the “humour” represented by each character – Knowell helps by criticizing each entrant as he meets them.