It may seem that the Buddha's teaching on emptiness is incompatible with his teaching on karma, which connects the result of an action with the same being who performed it. But actually, the two teachings need each other to make sense.
The five aggregates of form, feeling, perception, formations, and consciousness are empty in two ways. There is no ongoing self in the center, which points to the emptiness of self. All the aggregates are insubstantial, which points to the emptiness of all phenomena.
