FORRESTER, Jay (b. July 14, 1918, Anselmo, ne, usa) – American scholar and professor at the Massachusetts Institute of Technology (mit), the creator of system dynamics – theoretical foundations of global modeling.
In 1969, Forrester and his associates, in response to the Club of Rome’s proposal that a model of global development should be worked out, presented the model World-2 (W-2), which is built on the principles of system dynamics – a method of studying complex systems with nonlinear feedbacks that was developed at mit from the beginning of 1960s. Relying on the theory of information feedback systems he developed from the beginning of the 1950s, studies of decision-making mechanisms, experimental modeling of complex processes using computers as a means of simulating the actual processes using mathematical models, Forrester created a new type of model – simulation models that combine the advantages of analog and mathematical models.
According to Forrester, the industrial enterprise, the modern city, the world in general are complex systems, the relationship between the elements of which are essentially nonlinear and cannot be described by linear functions; therefore the analytical apparatus of mathematics, adapted to the study of linear dependencies of simple systems, cannot be applied to them. Forrester emphasizes that the processes occurring in complex systems do not allow for precise unambiguous description, as they are not strictly determined, stochastic. The elements of complex systems affect each other, generating a lot of positive and negative feedback loops. The condition of any item at any given time is determined not only by the entire set of interactions of other elements, but the whole history of the system. The parts of a complex system are in turn systems of a lower order of complexity. Forrester notes that a complex system, its components, and elements are characterized by a state of stable equilibrium. In its behavior the complex system is counterintuitive. The elements of the complex system do not change as a direct result of a local effect. The change of an item occurs when a number of impacts within a certain time interval reach a critical level. When the critical level is near, even the slightest pressure on the system is able to stimulate its radical transformation. The basic concepts of simulation modeling are level and pace.
The notion of “level” reflects the relationship between the discreteness of meanings and the continuity of their accumulation and is close in content to the concept of phase coordinates, which is used to construct formal models of dynamic processes. The concept of “pace” focuses on the dynamics of complex systems, describing the ratio of the first derivative (usually the time parameter) to the original function (for example, acceleration to speed). It is required that a change of levels causes the change of pace, and to indicate the time interval, Forrester introduces the term “delay” (“lag”).
He believes that to describe a dynamic system it is necessary to analyze the dependence of pace on levels, to build a system of causality. Simulation methods are not as elegant and concise as mathematical ones, but, according to Forrester, they have greater heuristic power, as a meaningful model is able to penetrate the deepest essential levels of the complex system.
The simulation model as opposed to the mathematical one needs no substantial restructuring of its units when there is interference in its work at any stage of the modeling (reconstruction, insertion, replacement, or removal of blocks). The structure of the simulation model is not dependent on the accuracy of the original data and the nature of the variables that are used.
The simulation model is ideally suited to the practice of system analysis application and the study of complex systems. The model has a high degree of generality. To get results, you need to clearly define the basic theoretical assumptions on which it is created. Forrester’s contribution to global modeling is that, despite the specific type of social system described by his model (a single industrial enterprise or a entire city), general patterns are traced after main results have been obtained.
The simpler, more transparent the structure of the model is, the more fundamental the patterns are which are taken into account in its creation.
This determines the validity and generality of the results. System dynamics is a tool that allows experts in specific fields of knowledge who do not have special training in the field of control theory and the theory of complex systems to successfully build models of processes that are of interest to them, and use them to understand more deeply the qualitative behavior of complex systems.
Forrester points out that the simulation cannot be used as a method of prediction of certain events at a certain time or a guarantee of the correctness of a decision.
It only helps to better understand the control process and to take successful decisions, but does not guarantee their absolute correctness.
At the same time Forrester’s works are characterized by unjustified absolutization of modeling as a universal method of cognition.
Forrester ignores the specificity of extrapolation methods, analogy, and experiment, treating them as special cases of simulation.
The social system, according to Forrester, also belongs to the class of complex counterintuitive nonlinear systems with numerous feedback loops.
Man cannot comprehend how social systems function, or clearly identify possible consequences arising from incomplete, vague, inaccurately articulated mental models.
Forrester emphasizes that any attempts to expand traditional theoretical understanding and to provide practical solutions to urgent problems that are beyond the control of civilization are fruitless.
Forrester develops W.R. Ashby’s idea of the need to use a cybernetic amplifier of human thinking abilities in analyzing these processes.
In World Dynamics (1971), Forrester proposes a preliminary, methodological model of the world.
The world appears to him as a whole, a complex system of different, interrelated levels (six phase variables) – people, time, funds in industry, assets in agriculture, natural resources, environmental pollution. In this case the absolute values are population size and time.
In World Dynamics, Forrester formulates the basic ideas of the theory of “limits to growth.” By simply displaying the real economic situation, Forrester offers not a model of economic development, but of extensive growth.
Experiments with this model allow him to conclude that extensive growth cannot continue indefinitely, as it has “physical limits” and is contradictory in nature.
Natural resources cannot grow, the areas suitable for agricultural cultivation of land are limited; crop yield and the saving of raw materials increase in arithmetical progression, while population, consumption, and pollution in geometric progression.
The peak of living standards was irreversibly passed by mankind in the mid-1950s, says Forrester.
If the exponential growth of the basic parameters of the economic organism continues, in the middle of the twenty-first century there will inevitably be a crisis in relations between society and nature.
The inertia of biospheric processes temporarily hides the scale of the impending crisis. Forrester defines the functioning of the global system as a spontaneous process, and considers any conscious intervention as a factor that will destabilize the system.
Considering the alternatives for the future development of mankind, the degradation of society and the environment, the total regulation of fertility, the rate of consumption and production, which cast doubt on the very possibility of personal freedom, Forrester chooses another option. By analogy with the evolution of natural populations, he sees the solution to the current situation as a transition by society itself to some higher equilibrium level.
His main conclusion is the need to harmonize human activities with the capabilities of the biosphere. The functioning of society in equilibrium can be achieved by stabilizing population growth, whereby advanced planning tools and new technologies are used to compensate for pollution by way of artificial and natural self-cleaning of the environment.
Forrester’s contribution to scientific knowledge consists of the creation of a model that shows that it is possible in the main to translate into the language of formal models the verbal models that exist in research, and to obtain quantitative estimates where previously only qualitative categories were used.
Forrester offers a convenient and efficient method of treatment of expert judgments, preparing the issue to the required level of detail and eliminating the need for bulky data banks.
All Forrester’s works are devoted to complex and poorly formalized issues and not only contain an attempt to their quantitative estimate, but they are a creative and intensive search for alternative methods of social development within economic processes around which common environmental parameters have evolved.
The basic methodological principles of global modeling, developed by Forrester, were the basis of projects undertaken by D. Meadows, M. Mesarovic, and E. Pestel, the Latin American project of A. Errera, and projects by Y. Kay, H. Linnemann, J. Tinbergen, and V. Leontiev. Forrester’s works significantly influenced the nature of scientific thinking in the last decades of the twentieth century.