 Gilbert has long held that participants in shared activity are obligated to do their part in it. Take her well-known example of walking together, starring Jack and Sue. When Jack does something that’s not compatible with walking together, e.g. walking so fast that Sue cannot keep up, Sue is entitled to rebuke Jack. This suggests to Gilbert that it is essential to shared activity (and intention) that each participant has an obligation to do his or her part in the activity (or in carrying out the intention). For example,