What kind of character is Mr Dumby in Lady Windermere's fan?

Although he doesn't do very much, Dumby serves an important role in Lady Windemere's Fan as he can be seen to keep the momentum of the play going. He doesn't partake in very much of the conversation, however when he does it is to plant seeds or some kind in the other character's heads.

Dumby can bee seen as the voice of Oscar Wilde within the play. The voice of reason, perhaps?