PIP: Economists are very much interested in theories of impossibility, especially in those that demonstrate that it is impossible for the world economy to increase to the point of solving poverty and the environmental degradation. In its physical aspects, the economy is an open subsystem of the terrestrial ecosystem, which is finite in material resources. As the economic subsystem grows, it incorporates an increasing proportion of the total ecosystem. For this reason, development is not sustainable. The term sustainable development, as it applies to the economy, is a contradiction. The economists claim that the growth of the gross national product is a combination of quantitative and qualitative increase and is not subject to the laws of physics. They are right to some degree, because growth means natural material increase by assimilating accretion, while development denotes expansion to slowly realize the opportunities for a state of conditions that are more, bigger, or better. When something grows, size increases. However, when something develops, different things happen. The terrestrial ecosystem develops but does not grow. Its subsystem, the economy, can continue to develop. Thus, sustainable development means development without growth, qualitative improvement which maintains the interchange of material-energy found within regenerative capacities of the ecosystem. In fact, the term sustainable development utilizes as a synonym the contradiction of sustainable growth. Politically, it is very difficult to admit that growth has its limits. The earth will not tolerate the multiplication of grain harvests 64 times only because in the last centuries a culture has developed that depends on exponential growth for its economic stability. The growth of agricultural plants is not sustainable. For plants there is a limit that the earth can support, as there is a limit for humans and cars, with dire consequences for those who ignore this fact.