In analyzing a behavioral engineering task, the engineer must determine: exactly what behavior he wants to occur, what stimuli are to control it, and what reinforcers are available. A behavioral engineer's definition of stimulus control is a simple one: Stimulus control exists to the extent that the presence or absence of a stimulus controls the probability of a response. From a behavioral engineering standpoint, a child is reading objects as soon as he can discriminatively respond to them. Once a child has begun to read, no one knows, really, how fast his education may proceed. Behavioral engineering certainly has no tools for dealing directly with a whole repertoire at once. But if we behavioral engineers take seriously what Keller and Schoenfeld and Skinner have said about what joy is, we can reduce the joy problem to manageable size. Joy is difficult to define, but perhaps even more difficult is love.