The debates on development manifest an increasing concern for sustainability, but as yet little awareness of the hierarchy in the ideas through which humans contribute to the problem. This gap is widened by a widespread but nevertheless unnecessary acceptance of unreasonable elements such as paradoxes, or the general fragmentation in knowledge, or allegedly general limits to it. First the character of such impediments is assessed, partly in theoretical considerations and partly through examples. This analysis reveals the root of a widespread self-limitation in thinking. Understanding its structure allows to synthesize an approach in which the problems do on principle not arise. It is conceptually precise but nevertheless universally applicable within the chosen query perspective, and hence useful for unifying knowledge toward a general sustainability of development.