Letter to William T. Powers

Eugene, Oregon
July 2003

Brother Bill:

I have thought about what I could put on paper that might be suitable for your festschrift. I thought, for example, of writing an essay on what it means to be called an expert—what an expert can and cannot do for the rest of us. After all, you and I are both experts. Unfortunately, I found myself doubting I could finish writing a decent piece by June.

I think both my last two books—Casting Nets and Testing Specimens” and “People As Living Things—can be interpreted as appreciations of your contributions to science and to good will toward humankind. For your festschrift, I quote below the coda from Chapter 18 of “People As.”

Phil Runkel


Having [read] this far, I think you can take a deep breath, look around in your thoughts, and see the grandeur of perceptual control theory.

I began reading the writings of W. T. Powers and his followers about 1985. As I read and pondered, I found my previous views undergoing wrenching and even frightening changes. I found myself having to disown hundreds, maybe thousands of pages of my writings that I had broadcast to my peers with pride. I found, then, that I could see order among my previous confusions about psychological method. The sword that cut the Gordian knot––that cut through my gallimaufry of methodological embarrassments––was the distinction between counting instances of acts, on the one hand, and making a tangible, working model of individual functioning, on the other. That idea, which in retrospect seems a simple one, was enough to dissipate about 30 years of daily dissatisfaction with textbook methods of psychological research. That simple bifurcation is what I wrote about in my 1990 book.

The idea that permits making tangible, working models is, of course, the negative feedback loop. And that, in turn, requires abandoning the almost universally unquestioned assumption made by most people (including psychologists) of straight-line causation––which, in turn, includes the conceptions of beginning and ending. Displacing that theoretical baggage, the negative feedback loop requires circular causation, with every function in the loop performing as both cause and effect. That, in turn, implies continuous functioning (beginnings and endings are relegated to the convenience of perception at the fifth level). One cannot have it both ways. Living creatures do not loop on Mondays and straight-line on Tuesdays. They do not turn the page with loops while reading the print in linear cause-to-effect episodes. William of Occam would not approve.

Powers did not invent the loop. It existed in a few mechanical devices in antiquity and came to engineering fruition after electrical devices had become common. Some psychologists even wrote, haltingly, about "feedback." But the manner in which living organisms make use of the feedback loop––or I could say the manner in which the feedback loop enabled living creatures to come into being––that insight was Powers's alone. That insight by itself should be sufficient to put Powers into the pages of the history books as the founder of the science of psychology. Historians of psychology will, I think, come to name the year 1960 (when the two articles by Powers, Clark, and McFarland appeared in Perceptual and Motor Skills) as the beginning of the modern era. Maybe the historians will call that year the Great Divide. The period before 1960 will be treated much as historians of chemistry treat the period before Lavoisier brought quantification to that science.

Using the negative feedback loop as the building-block of PCT enabled Powers to show how mathematics could be used in psychological theorizing. Powers's true use of numbers made it possible at last to test theory by the quantitative degree to which the data from any single individual approach the limits of measurement error, as in other sciences.

Even making a science possible was not enough to fill the compass of Powers's vision. He saw the unity of all aspects of human perception and action. He saw that there was not a sensory psychology over here, a cognitive over there, a personality in this direction, a social in that, and so on, but simply a psychology. He gathered every previous fragment into one grand theoretical structure––the neural hierarchy. The nature of the particular levels is not crucial. What is crucial is the idea of the enabling effect of organization by levels––the enabling of coordination among actions of all kinds. Previously disparate psychologies with disparate theories can now all begin with the same core of theoretical assumptions. Though it will take a long time to invent ways of testing the functioning of the hierarchy at the higher levels, I find it exhilarating to realize that Powers and others have already built models having two or three levels organized in the manner of hierarchical control and that those models actually work.

The neural hierarchy is far more than a listing of nice-sounding categories. The theory itself tells how we can recognize the relatively higher and lower placements of levels. It tells us, too, some of the kinds of difficulties to be anticipated in doing research at the higher levels. That kind of help from early theory is a remarkable achievement.

I have mentioned three momentous insights: (1) that the negative feedback loop is the prerequisite for life, (2) that numbers should be used to show the approximation of model to human individual, and (3) that control grasps more aspects of the environment through its hierarchical structure. For any one of those three momentous insights, I think Powers deserves a bronze statue in the town square. To put all three together in one grand system concept is the kind of thing that happens in a scientific field once in a century or more.

After more than 15 years of reading, conversing, writing, and thinking about PCT almost every day, I still feel the way Lewis and Clark must have felt when they began rowing their boats up the Missouri River. I know the general nature of the territory, I know that much of what I will come upon will be astonishing and baffling, and I know that every mile of the journey will be hard going. As I write this book, most parts of which are simply elaborations of the three simple ideas set out above, I find time and again that I must take an hour or a day to struggle with ways of keeping the words as simple as the idea. The ramifications of those simple ideas are multifarious and subtle. As I begin to describe a complication in the way those ideas work together, I find now and again that I have opened further regions of complexity for which I am wholly unprepared. Then I must take an hour or a day or a week to find my way back to firm footing. I do not feel that I am trudging along a prescribed path. I feel that I am taking every step with caution, but also with awe and exhilaration as I wonder what I might add to my understanding. I am sure, however, that I have only an inkling of the exploratory feelings Powers must have had as, day by day and year by year, he built his theory. He guided his footfalls by experimentation; I have guided mine only with thinking about the steps he took.