In this paper we examine the use of hypotheticals as a heuristic device to assist a case-based reasoner test the strengths, weaknesses, and ramifications of an analysis or argument by exploring and augmenting the space of known cases and indirectly, the attendant spaces of doctrine and argument. Our program, HYPO, works in the task domain of the law, particularly, the area of trade secret protection for software. We describe how HYPO generates a constellation of legally-meaningful hypothetical fact situations ("hypos") which are "near" a given fact situation. This is done in two steps: analysis of the given situation and then generation of the hypos. We discuss the heuristics HYPO currently uses, which include: (1) make a case weaker or stronger; (2) generate an extreme case; (3) enable a near miss; (4) manipulate a near win; and (5) generate a case on a related "dimension".