review -- The Restless Clock: A History of the Centuries-Long Argument over What Makes Living Things Tick by Jessica Riskin

In The Restless Clock Stanford Professor of History Jessica Riskin suggests there might be a flaw in how explanations are done in the life sciences, perhaps even in all the sciences. The current model, which she finds incomplete, treats all of nature as a machine whose parts are made of passive, inert matter, moving only when set in motion by external forces. Natural entities are themselves viewed as empty of any active power of their own, of any force, will, purpose, self-direction, self-organization, any trace of what she calls in general “agency.” In order to challenge this paradigm, which she characterizes as "brute mechanistic" or "passive mechanistic," she reviews the history of modern science since the seventeenth century, showing how this dominant view has always been shadowed by alternate views explaining nature in terms that do include agency.

The passive mechanistic model was established during the seventeenth century, but not only as a foundation for purely rational, mechanistic explanations of the world. There was also a religious dimension to regarding nature as a machine, a gigantic clockwork. To the thinkers of that time the wondrous complexity of nature and the marvelous fitness of all its parts required a Great Designer existing outside nature — thus, the Argument from Design. Also, if there was no force within nature responsible for its motion and organization, the force must be outside, in other words, a God winding up the great clock of the universe. Riskin believes that science today, secular and at the same time denying agency in nature, is failing to explain the origin of motion and organization in nature.

As a prime example of an early attempt at describing nature as containing its own agency (which she calls "active mechanism"), she offers a quote from Leibniz. He reinterpreted the idea of a clock as something more than a passive device deriving its activity solely from outside forces, and he provided her the title for her book. “In German,“ Leibniz wrote, “the name for the balance of a clock is Unruhe—that is to say disquiet. One could say that it is the same thing with our body, which can never be perfectly at ease: because, if it were, a new impression of objects, a little change in the organs, in the vessels and viscera, would change the balance and make these parts exert some small effort to get back to the best state possible; which produces a perpetual conflict that is, so to speak, the disquiet of our Clock.” Leibniz's clock is a mechanism, explainable in terms of its component parts, but self-organizing under the power of its own balance, a mechanism with agency, a restless clock.

The Restless Clock gives a detailed discussion of the interaction of theories of passive and active mechanism over a period of more than three hundred years. An astonishing number of cases are covered, from Descartes, Leibniz, and Lamarck to John von Neumann, Stephen Jay Gould and Ray Kurzweil, with dozens more in between. The issue shows up not fully resolved even in the chapter on Darwin who, while usually adamant in rejecting agency in nature, nevertheless lapsed occasionally, admitting the existence of natural powers such as “tendencies” or the innate power to vary.

What would it mean to include agency in scientific explanations? Riskin offers only a few suggestions, such as a heliotropic plant following the path of the sun or electrons moving to conserve charge. But she points out that, in fact, even now scientists often use language that suggests agency: they speak of cells wanting to move toward a wound, proteins regulating cell divisions, or genes dictating the production of enzymes. Scientists insist that such phrases are mere figures of speech, shorthand taking the place of a complete, rigorous, passive-mechanistic description. If that rigorous explanation is not known today, they maintain, it will be found in the future. That hope, according to Riskin, is an article of faith, not of science. She suggests, instead, that agency be given a place in scientific explanations as “a primitive feature of the natural world like force or matter, an aspect of the very stuff of nature’s machinery, and especially its living machinery.” 

The final chapter focuses on an influential treatise by Erwin Schrödinger, a founder of quantum physics. In “What Is Life?” he argued, first, that a living creature is a machine by definition in that it produces and maintains order. “Schrödinger explained that molecules were configurations of atoms occupying their lowest energy level. In order to change configurations, they needed to receive at least a minimum quantum of energy. The stability of a molecule could perhaps account for the order-producing capacity of genes, responsible for maintaining the structure of living organisms both within individuals and across generations.” But Schrödinger goes on to claim that a living creature is more than a machine; it is essentially an agent because, by means of its action of eating, drinking, breathing, photosynthesizing, and so forth, it resists entropy — it avoids decaying into equilibrium. A living creature is thus a clock — but a restless one, a machine with agency.

Despite its detailed scholarship — or perhaps because of it — The Restless Clock is unlikely to win many overnight converts. It winds its way through innumerable theories, debates, and descriptions, through many people, a great deal of biographical material, but with little effort made to tie the pieces together, to summarize, to reveal an overall pattern. The impression is often of a catalogue rather than an argument.

However, if nothing else, as theory piles upon theory, and one debate shades into another, the book certainly illustrates how terribly difficult it has been for civilization to sort out such a jumble of ideas and arrive at the understanding of the world we now have. And along the way it unearths a truly astonishing collection of historical curiosities.

It even has moments of comedy, as when it describes many elaborate mechanical systems that royalty and other high-ranking Europeans constructed on their grounds in the late medieval and early Renaissance periods. These perceiving and responsive machines were able to sense the presence of people and react to them, for example, tempting visitors to pause before a beautiful scene, then bombarding them with a cloud of flour or spraying them with water from hidden pipes, or luring them to sit on a bench, then soaking their bottoms. It was comedy, but it also marked the beginning of machines exhibiting humanlike capabilities.