More important here than the differences between these variations is what they have in common. At its simplest, a system is something composed of parts but which adds up to more than just these parts. It may be a natural system, an engineered system or a purposeful human-activity system. A human body or an ocean can be seen as a system; and so can a car or a computer. A company can also be described as a system, as can a market, and both as subsystems of the larger system that is an economy. A hospital and the NHS are also systems. So systems thinking is about ‘joined-up-ness‘, and from this interconnectedness flow several important consequences. One is the need to consider the parts not on their own, but in relation to the whole. The poor results of managing the parts rather than the whole—of not using systems thinking, in fact—are perhaps most familiar in service delivery, irrespective of whether public or private.