What is that which happens aside from the main design; an accidental or subordinate action or event. No person, no incident, in a play but must be of use to carry on the main design. Dryden called?

incident — That which happens aside from the main design; an accidental or subordinate action or event. No person, no incident, in a play but must be of use to carry on the main design. Dryden. (Webster's 1913.)