Chance is a new event/situation with significant impact on an agent's decision making, that is, either an opportunity or a risk. In this paper, suggesting the modern scope of dynamic planning as a typical stage on which Chance Discovery and Management (CD&M) play a special role, we abstract `chance' into three essentia ls, which provide not only its conceptual criteria but also methodological clarifications in a BDI (Belief-Desire-Intention Agent Theory [Georgeff et al., 1998]) viewpoint. By proposing a theory of Perception and its architecture integrated with IRMA, and a logical system for detecting motivational correlation, we suggest that a chance is an event/situation perceived or conceived outside an agent's previous anticipation, while inside (partially at least) control of her particip ation, and revealed by its correlation with her motivational attitudes as Desire and Intention.