If the society toward which we are developing is not to be a nightmare of exhaustion, we must use the interlude of the present era to develop a new technology which is based on a circular flow of materials such that the only sources of man's provisions will be his own waste products.

One advantage of exhibiting a hierarchy of systems in this way is that it gives us some idea of the present gaps in both theoretical and empirical knowledge. Adequate theoretical models extend up to about the fourth level, and not much beyond. Empirical knowledge is deficient at practically all levels.

Humble, honest, ignorance is one of the finest flowers of the human spirit

... the fouling of the nest which has been typical of man's activity in the past on a local scale now seems to be extending to the whole world society.

Mathematicians themselves set up standards of generality and elegance in their exposition which are a bar to understand.

Don't go to great trouble to optimize something that never should be done at all. Aim to enhance total systems properties, such as creativity, stability, diversity, resilience, and sustainability - whether they are easily measured or not.

Conflict may be defined as a situation of competition in which the parties are aware of the incompatibility of potential future positions, and in which each party wishes to occupy a position that is incompatible with the wishes of the other.