Typical was a negative review of The Limits to Growth in the New York Times, written by Peter Passell, a Columbia University economist, and two Harvard University economists named Marc Roberts and Leonard Ross. The Limits to Growth, they said, was “empty and misleading,” based on an “intellectual Rube Goldberg device,” full of “arbitrary conclusions that [had] the ring of science,” but were really “less than pseudoscience.” Dr. Passell, now editor of the Milken Institute Review, hasn’t softened his opinion, though he allows there is a place in the world for modeling. “Simulation is always a problem,” he says. “You’ve got to be very disciplined so you understand what the model is sensitive to. Professor Forrester and that crowd were oblivious to the reductiveness of their process.”
At the heart of the debate over limits to growth is an unanswered question: Are planetary overshoot and collapse inevitable? Or can we rely on human ingenuity, economic forces, and technological advancement to mitigate the effects? Neither side has backed down. Bjorn Lomborg, for example, set up much of his book The Skeptical Environmentalist as an attack on the Limits to Growth mind-set, arguing, for example, that pollution levels and population growth rates have declined. But in a 30-year update to The Limits to Growth published in 2004 (three years after Donella Meadows passed away), the authors conclude that most statistics (including those for global climate change) are still playing out as the model predicted, that runaway growth has remained consistent with their model, and that growth restraints should remain an important element of global policy. Of his still-vocal critics, Professor Forrester says, “I don’t really expect to convert them. The only option is to outlive them.”
Dynamics versus Thinking
By the mid-1980s, a group of Professor Forrester’s former students had recast his stock-and-flow notation into a set of “archetypes”: common system patterns that showed up again and again in a variety of situations. The Limits to Growth was the basis of one of these archetypes; although it was famous as a warning to industrial society, it also applied to many innovative corporate initiatives, which tended to hit a wall and collapse just when it seemed that they were about to break through into success. Another common archetype, “Eroding Goals,” charted the course of many companies that respond to competition by lowering the quality of their offerings, until they can no longer match their original premium identity. Peter Senge, then an instructor at MIT, captured several of the archetypes and a simplified explanation of the system dynamics approach in The Fifth Discipline. That book, which has sold 2 million copies worldwide, is far easier to read than anything penned by Jay Forrester. But it also makes a distinction that Professor Forrester himself rejects: between “system dynamics,” which requires constructing and testing electronic simulations, and “systems thinking,” which draws people into conversation to consider the same types of systemic situations in depth.
Jay Forrester confesses to a certain ambivalence about Dr. Senge’s book. He is glad of its success, but disappointed that the book doesn’t adequately explore the assumptions that went into the models underlying the archetypes. “The trouble with systems thinking,” he says, “is it allows you to misjudge a system. You have this high-order, nonlinear, dynamic system in front of you as a diagram on the page. You presume you can understand its behavior by looking at it, and there’s simply nobody who can do that.”
For his part, Dr. Senge says his mentor’s concern is justified, but there is still a value in introducing systems thinking to people who may never go on to system dynamics. “Jay has always been focused on the high ground, training people who can develop advanced simulation models,” Dr. Senge says. “I think that’s great, but it takes years, and I grew impatient with this very long-term strategy. It is also useful to train people to do first aid, rather than to only develop physicians.”