The strongest criticism has come from some economists. The objections range from simple misunderstanding, through belief that essential structures ha… - Jay Wright Forrester

In spite of the tentative nature of the world model described here, various conclusions are drawn from it. Man acts at all times on the models he has available. Mental images are models. We are now using those mental models as a basis for action. Anyone who proposes a policy, law, or course of action is doing so on the basis of the model in which he, at that time, has the greatest confidence. Having defined with care the model contained herein, and having examined its dynamic behavior and implications, I have greater confidence in this world system model than in others that I now have available. Therefore, this is the model I should use for recommending actions. Those others who find this model more persuasive than the one they are now using presumably will wish to employ it until a better model becomes available.

It is to be hoped that those who believe they already have some different model that is more valid will present it in the same explicit detail, so that its assumptions and consequences can be examined and compared. To reject this model because of its shortcomings without offering concrete and tangible alternatives would be equivalent to asking that time be stopped. But the world will continue to turn. We always use the most acceptable model at any point in time. But how should we proceed so that the most acceptable model is also the best one that is available? We should try for three things. First, the best existing model should be identified at each point in time. Second, the best currently existing model should be used in preference to traditional models that may be less clear and less correct. Third, aggressive effort should be devoted to a continual improvement in the available models of the world system.

The enterprise engineer must be a leader, a designer, and a synthesizer. He is a doer. He understands theory as a guide to practice. He must concern himself with human organization because the pace and success of technology are becoming more dependent on interaction with the social system and less on scientific discovery. In private as well as public research and development, such men must find ways to reverse the deterioration of ethics and efficiency. They will strengthen the information links between physical design and the public so that technology can better serve society. In the public sector they must show the level of wisdom and leadership that can co-ordinate great engineering projects with politics. They will recognise that informing the public and becoming a nucleus for crystallising public opinion is even more important in many programmes than is the underlying science.