We make our tools, and then they shape us.

[The historical] development in the international system may almost be defined as the process by which we pass from stable war to stable peace.

As long as man was small in numbers and limited in technology, he could realistically regard the earth as an infinite reservoir, an infinite source of inputs and an infinite cesspool for outputs. Today we can no longer make this assumption. Earth has become a space ship, not only in our imagination but also in the hard realities of the social, biological, and physical system in which man is enmeshed.

The world moves into the future as a result of decisions, not as a result of plans. Plans are significant only insofar as they affect decisions.

It is clear that the building of models is not a purely mechanical process but requires skill of a high order - not merely mathematical skill but a sensitivity to the relative importance of different factors and a critical, almost an artistic, faculty in the selection of behaviour equations which are reasonable, tentative hypotheses in explaining the behaviour of actual economies.

Nothing fails like success because we don't learn from it. We learn only from failure.

The evolutionary vision is agnostic in regard to systems in the universe of greater complexity than those of which human beings have clear knowledge.