The Restless Clock: A History of the Centuries-Long Argument over What Makes Living Things Tick by Jessica Riskin. Univ. of Chicago Press, 548 pages, $40.

When two aspiring young writers meet and circle each other at a party in Boston, Brooklyn, or Berkeley, sooner or later (usually sooner) one will ask: "Do you have an agent?" Without one, every hopeful writer knows, you're nowhere: editors nowadays are too beleaguered to read anything not vouched for by someone whose commercial judgment has been tested and vindicated in the literary marketplace.

According to the delightful science-fiction romance Her (2013), artificial intelligences also socialize, or will before long. I imagine them asking one another at parties, "Are you an agent?" They will not, of course, be asking about literary representation but about the psychological or emotional or moral capacity we commonly call "agency." They'll be looking to find out whether the AI they're meeting answers ultimately to itself or to someone else, whether it can set and change its own goals, whether it can surprise itself and others. Beings possessed of agency are autonomous, spontaneous, capable of initiative, and moved by internal as well as external forces or drives. Agents are usually considered much more fun to be in a relationship with than non-agents.

According to Jessica Riskin's The Restless Clock, agency is everywhere, or at least far more widespread than is dreamt of in modern philosophy of science. If agency is "an intrinsic capacity to act in the world,"[1] then science is not having any. It is "a founding principle of modern science ... that a scientific explanation must not attribute will or agency to natural phenomena."[2] This "ban on agency" is the foundation of scientific epistemology; it "seems as close to the heart of what science is as any scientific rule or principle."[3]

Of course, scientists constantly write and speak as if natural phenomena had purpose and intentions: proteins "regulate" cell division; some cells "harvest" energy; genes "dictate" myriad biochemical activities. But this anthropomorphizing language is just a convenience, a placeholder. As a biologist friend assures Riskin: "The more we get to know, the less these phenomena will seem purposeful."[4] Pressed, her friend laughs nervously and confesses: "OK, you're right; it's a matter of faith. And, as with any matter of faith, I am absolutely unwilling to admit that I'm wrong. I know that if I knew everything about the processes I study, I would have no reason to appeal to agencies of any kind, even as a manner of speaking, let alone as an explanation."[5]

Centuries of debate - largely occluded thanks to the theoretical and institutional hegemony of one side - have issued in this "quandary," Riskin argues. On one side of this debate, espoused by Riskin's biologist friend, is a conception of nature as a "brute" or "passive" mechanism, lacking agency and susceptible of entirely non-teleological explanations. The other, much less familiar tradition sees nature as an "active" mechanism, wholly material yet also "restless, agitated, responsive, purposeful, sentient," as "self-constituting and self-transforming machinery."[6] Ranging over Western (and occasionally non-Western) intellectual history from Aristotle's treatises on animals to current controversies in evolutionary theory and cognitive science, The Restless Clock undertakes, with astonishing energy and resourcefulness, to excavate this debate and expound its significance.

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In the Middle Ages, Europe was dotted with automata - saints, angels, devils, and monks in churches and cloisters as well as festivals and marketplaces; knights, ladies, animals, and mythological figures in castles and gardens; and timepieces of every variety. Some of these figures were marvelously elaborate. In the Benedictine Abbey at Cluny, a mechanical cock

flapped and crowed on the hour ... Meanwhile, an angel opened  a door to bow before the Virgin; a white dove representing the Holy Spirit flew down and was blessed by the Eternal Father; and fantastic creatures emerged to stick out their tongues and roll their eyes before retreating inside the clock.[7]

Even more remarkable was the clockworks of the Strasbourg Cathedral.

For nearly five centuries, the Strasbourg Rooster cocked its head, flapped its wings, and crowed on the hour atop the Clock of the Three Kings, originally built between 1352 and 1354, and refurbished by the clockmaker brothers Isaac and Josias Habrecht between 1540 and 1574. Beneath the Rooster, the astrolabe turned and the Magi scene played out its familiar sequence. In the Habrecht version, the Rooster, Magi, Virgin, and Child were joined by a host of other automata: a rotation of Roman gods who indicated the day of the week; an angel who raised her wand as the hour was rung, and another who turned her hourglass on the quarter hour; a baby, a youth, a soldier, and an old man representing the four stages of life, who rang the quarter hours; and above them, a mechanical Christ came forth after the old man finished ringing the final quarter hour, but then retreated to make way for Death to strike the hour with a bone.[8]

The Catholic Church was an enthusiastic patron of these automata, as well as of translations of ancient texts on mechanical engineering, which inspired Christian craftsmen. From this robust appetite for dramatic embodiments of virtue, vice, and divine love, Riskin deduces that medieval Catholicism "held no sharp distinction between the material and the spiritual, earthly and divine."[9] Scholastic theology endowed non-human life with "vegetative" and "nutritive" souls, and the Great Chain of Being emphasized the relatedness of all creation, from ants to angels.

Reformation theology, reacting against this ontological permissiveness and Southern European earthiness, which it perceived as a profanation of the sacred and a source of rampant ecclesiastical corruption, discouraged icons, rejected the Eucharistic doctrine of transubstantiation, and favored a more austere form of piety, emphasizing God's otherness and dispensing with saintly and angelic intermediaries. The grand panoply of pious and secular automata went "from being manifestations of spirit and liveliness to being fraudulent heaps of inert parts."[10] Matter and mechanism were no longer taken to be active and vital but instead inert and passive.

This radical separation of spirit and matter formed the intellectual backdrop of the seventeenth-century scientific revolution. Nature was conceived of as a vast machine which, like all machines in the new Reformation cosmogony, could only be set in motion by an external source: God. Descartes initiated the revolution in philosophy by relocating the self from the medieval animated body to an immaterial soul. "The Cartesian removal of soul from the machinery of the world, like the Reformist removal of God from nature, left behind something starkly different. ... The animal-machine, as Descartes described it in the first instance, was warm, mobile, living, responsive, and sentient. The same living machinery, when measured against a disembodied, transcendent self, looked different: confined, rote, passive."[11]

This was not altogether Descartes' intention. Riskin surveys the response to Cartesianism in fascinating detail, showing how one interpretation prevailed: that Descartes had "demonstrated God's existence by detailing the mechanical perfection of his artifact, the world-machine."[12] Although it was embraced by Malebranche, Buffon, Boyle, Hobbes, Locke, Newton, and other dominant figures in early modern intellectual history, Descartes, she contends, would have rejected this "new tradition of natural theology,"[13] with its watchmaker God.

So did quite a few others, though their arguments have largely been lost to view, as is often the case with unorthodox intellectual traditions. One was the celebrated physiologist William Harvey, who taught that animals and even the internal organs of human beings harbored "forms" that solved problems, took initiatives, and allowed for "a rising of mechanical parts to new powers."[14] His Oxford colleague Thomas Willis described bodies as "vital, perceptive, active animal-machines,"[15] not passive but self-moving.

The best-known and most thoroughgoing exponent of "active mechanism" was Leibniz. Convinced that the closed mechanical systems described by Boyle and Newton admitted of no explanation for motion and change, Leibniz posited a vis viva, a living or vital force. It was a "metaphysical" thing, a "principle underlying all material events." Instead of impenetrable, indivisible, insentient atoms, he proposed that the fundamental units of matter were a species of "metaphysical points," with "something vital about them."[16] These were the "monads," elementary spiritual substances out of which more complex creatures were built up. The resulting entities were best described as "organized" rather than "designed"; their plan allowed for spontaneity and learning.

Leibniz found many followers among eighteenth-century physicists and engineers, including the Marquise du Châtelet, Lazare and Sadie Carnot, and others, but his reputation was lastingly deflated by Voltaire's satire Candide -  unfairly, Riskin protests, since his "pre-established harmony" was not at all the purblind optimism of Doctor Pangloss. Still, it is a bit difficult not to misunderstand Leibniz, even with the benefit of Riskin's exegeses. The materialists' "big mistake, he judged, was to assume that a mechanist science must eliminate incorporeal things, when in fact a mechanist science required incorporeal things. Leibniz was after a third way: ... a fully mechanist account of nature that included immaterial 'active force.'" The universe was "a great nesting of machines within machines within machines, all built out of little perceiving spirits." "I have at last shown," he wrote triumphantly, "that everything happens mechanically in nature, but that the principles of mechanism are metaphysical."[17] After considerable wrestling with these and other propositions of Leibniz, I am inclined to pardon Voltaire.

The philosophes, though enthusiastic materialists and defiant atheists, also found evidences of agency within both living creatures and machines. "Organization," according to La Mettrie, author of L'homme machine, "is the first merit of Man." Riskin elaborates: "An organized machine was a concurrence of active parts, unlike the rigidly deterministic, designed clockwork described by natural theologians."[18] The favored eighteenth-century metaphor was weaving; organisms were "self-moving looms," their bodies "self-weaving fabric."[19] Though Emerson and Carlyle believed that the legacy of the eighteenth century was a "dead world of atoms controlled by the laws of a dead causality,"[20] Riskin claims that a closer look at the philosophes' texts (along with Kant's, whose ideas about the philosophy of science she renders intelligible, even lively) reveals "a physical world imbued with perception, feeling, and self-organizing agency."[21]

"By the turn of the nineteenth century," Riskin writes, "a living being in scientific, philosophical, and literary understanding had become, in essence, an agent ... a thing in constant, self-generated motion and transformation of material arts ... 'striving' ... and respons[ive] to external circumstances."[22] Life was "a form of activity, a continual effort to constitute itself from and against dead matter."[23] In this intellectual climate, the science of biology - first named by Lamarck - came into being. Lamarck has been generally misunderstood, Riskin claims. The inheritance of acquired characteristics does not rely on a mysterious mental agency or a mystic elan vital. The life force, or pouvoir de la vie, was entirely material but not wholly passive, and its effects were not altogether random. In the course of their development, organisms responded to new challenges by evolving new capacities, sometimes by altering the environment to favor the selection of these capacities, and sometimes by changing the organism's hereditary material. The "pope" of late-nineteenth-century Darwinism, August Weismann, declared this impossible, formulating the still-prevalent doctrine that changes in an organism's physiology or environment can only affect its somatic cells, not its germ cells.

There is a long, semi-underground history of Lamarckian challenges to this Darwinian orthodoxy, beginning, Riskin suggests, with Darwin himself, who asserted the inheritance of acquired characteristics and hesitated, through all six editions of the Origin of Species, to omit all references to purpose and internally directed adaptations. Throughout the late nineteenth and early twentieth centuries, his successors - Weismann, His, Haeckel, Roux, Loeb, Stresemann, Driesh, De Vries, T.H. Morgan, D'Arcy Thompson - argued the mechanisms of biological causation back and forth, their arguments traced in heroic detail in The Restless Clock. The "neo-Darwinian synthesis" that emerged was a decisive victory for the passive mechanists, enshrining the principle that "agency cannot be a primitive, elemental feature of the natural world."[24]

The intuition that deterministic models of causation, at least as currently conceived, cannot fully explain the purposive behavior of living beings refuses to die, however. Riskin finds traces in two current debates: in cognitive science, between "embodied" and "computational" theories of intelligence; and in evolutionary biology, between "strict" and "modified" adaptationism. Frustratingly, both sides in both these debates explicitly disavow any recourse to individual agency or purpose as an explanatory strategy. But she draws hope from the unsettled state of both debates; from new sub-disciplines that are yet to be incorporated into the passive-mechanist consensus: Chomskyan linguistics and epigenetics; and from that bottomless wellspring of theoretical speculation, quantum uncertainty.

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The Restless Clock, though an extraordinary achievement, is naturally open to a few minor cavils. I think perhaps Riskin exaggerates the extent to which medieval Catholicism "held no sharp distinction between the material and spiritual" and to which "a rigorous distinction between divine spirit and brute matter" was an innovation of the Reformers. Though Scholastic philosophy, as she correctly points out, defined the soul as the "form" of the body, the difference was nevertheless absolute. A handbook of Catholic theology lists as de fide (i.e., to be believed on pain of excommunication) the doctrine that "Man consists of two essential parts - a material body and a spiritual soul."[25] It is true that the spirituality of the Latin Catholic countries during the Middle Ages was grossly materialistic indeed. But popular spirituality is not theology.

Riskin is clearly a partisan in the debates she reconstructs, but her judiciousness in reporting the arguments on both sides is exemplary. There is only one sentence in the book that might occasion a raised eyebrow. Discussing the Gould-Lewontin/Dawkins-Dennett debate over adaptationism, she writes: "[S]trict adaptationists, like the natural theologians of old, assumed that all structures in nature existed for reasons of optimal design, and that the orderings and arrangements of the natural world were therefore normatively correct and good."[26] The alleged inference is fallacious; the second half of the sentence does not follow from the first. Actually, it's not clear whose opinion the sentence conveys, Riskin's or Gould and Lewontin's. Either way, the accusation of Social Darwinism - for that is what it amounts to - seems to me out of place.

Notwithstanding all the enlightenment (and entertainment) I derived from The Restless Clock, I must confess to an even more fundamental dissatisfaction - whether with the book's argument or with my own power of comprehension, I am genuinely unsure. I feel a little like Mister Jones in one of our recent Nobel laureate's best-known songs: something is happening here, but I don't know what it is.[27] The insistent rhetoric of active versus passive, of "living force" versus "dead matter," of  "purpose," "striving," and "self-organization" versus "inert" and "brute" mechanism, has me quivering in agreement - but with what, exactly, I'm at something of a loss to say. Even after hundreds of pages of Riskin's painstaking exposition, I cannot quite get my mind around the difference between a world with agency and a world without it.

The book opens by recounting Thomas Huxley's celebrated joke, in a lecture of 1868, to the effect that we no more need a constitutive principle called "vitality" to explain life (or by extension, "agency" to explain action) than we need a constitutive principle called "aquosity" to explain water. Riskin does her best - which, as I hope I have duly acknowledged, is very good indeed - to suggest that the joke is on Huxley. But I'm not convinced. Recall her definition, also from the book's opening pages, of agency: "an intrinsic capacity to act in the world." I think I see what work "intrinsic" (though not "in the world") is meant to do in that sentence: to distinguish action whose cause is from within rather than from without, a rock from a squirrel. Does a rock, then, have an "extrinsic capacity to act"? It can roll if someone rolls it - but is that acting? Usually we say that a rock has no capacity to act unless acted on. So maybe the definition of agency should be "the capacity to act without being acted on." Of course, nothing is ever not being acted on somehow; and for that matter, everything inside anything was once outside it and will eventually be outside it again; and what's more, everything at every instant is so multifariously embedded in so many networks and hierarchies that "inside" and "outside" begin to look a bit dodgy. Perhaps we should just define agency as "capacity to act." And how do we identify this capacity? Initially we may assume that if it looks just like something else that acts, then it probably acts as well. But maybe it's only an exquisite copy. Unless it actually acts - somehow, anyhow, even just metabolizes - we can't know whether it has the capacity to act.

Hmm. I'm not sure, then, why we shouldn't conclude that "X has the capacity to act" (that is, "X has agency") doesn't mean anything more or less than "X acts (somehow or other, sometime or other)." "X has agency" adds no more to "X acts" than "X has dormitivity" adds to "X sleeps" - or than "X has aquosity" to "X is wet." If we know how something acts in every situation of interest to us, we'll have the answer to any question that the statement "X has agency" might be the answer to. Maybe Huxley had a point.

What about the "from within" part, the autonomy, spontaneity, responsibility, etc. that are supposedly entailed by agency? Those are useful words; there's no reason why we should give them up, any more than Riskin's biologist friend need feel sheepish about using words like "control," "regulate," or "dictate." With their help we can still worry the questions Riskin presumably wants us to, questions like: Can a complex machine act spontaneously? What emotions do other primates (cephalopods, cetacae, etc) feel? Are any plants conscious? How do proteins know just what to do? What can alter an organism's DNA? What affects how genes are expressed? But wouldn't two conscientious scientists, one a believer in active mechanism and one in passive mechanism, go about investigating these questions in exactly the same way, and mightn't they very well report exactly the same results? And if that's the case, do their philosophical beliefs matter? Isn't it only when they operate to close off inquiry prematurely - by saying, in effect, "just because" - that words like "will," "purpose," "mind," and "inner life" are unwelcome? Riskin would, I suppose, reply that the point of agency/teleology/self-organization talk is to generate new, otherwise unformulatable questions. Fine, but where are they?

Newly acquainted artificial intelligences (carbon-based ones, too) will undoubtedly continue to probe for assurance that their potential partners are fully (or at least sufficiently) aware of their own motives and in control of their own purposes. They will ask the same searching questions (since even those who use the language of "agency" will hardly be satisfied with a simple "Yes" in reply to the question "Are you an agent?"), listen for the same revealing intonations, watch for the same telltale gestures and expressions. A world with the term "agency" will look and feel exactly like a world without it, which means it is what William James (in one of his many moods) called the term "free will": a "fifth wheel to the coach."[28]

"Intellectual possibilities are not the sole fruits of this study," Riskin promises at the book's outset.

Social and political engagements ... have all along been inextricable from the competition between scientific models of living and human beings. The classical brute-mechanist approach to the science of life and the active-mechanist approach have developed, as we shall see, in close conjunction with mechanical and industrial arrangements such as the automatic loom and the transformed world of production that accompanied it; with economic policies including the division of various kinds of labor; with taxonomies and rankings of human beings by sex, race, class, geographical origin, and temperament; and with projects of imperial conquest and governance. In what follows, investigating this centuries-old dialectic in science will mean uncovering the hidden action of forces that are at once intellectual and political, scientific and social.[29]

Though the social and political implications hinted at here are not subsequently developed in much detail in The Restless Clock, there are echoes, in this passage and throughout the book, of a long and venerable tradition: the Romantic critique of science and technology, from William Blake to William Morris to Herbert Marcuse and beyond. For all its indispensable wisdom, that tradition has always seemed to me mistaken insofar as it seeks to impugn rather than supplement scientific rationalism. The habit of analysis may, as John Stuart Mill ruefully observed in his Autobiography, have "a tendency to wear away the feelings." But remedying this malaise, in our case as in Mill's, is not so much a matter of attacking a malignancy as of minimizing an inevitable imbalance. Undoubtedly, even the greatest scientist is not a complete human being. But then, there are no complete human beings.

One of Riskin's champions, the great American historian Jackson Lears, has written that the consequences of adopting her perspective "might be political and moral as well as intellectual. A full recognition of an animated material world could well trigger a deeper mode of environmental reform, a more sane and equitable model of economic growth, and even religious precepts that challenge the ethos of possessive individualism and mastery over nature."[30] The desirability - the stark urgency - of environmental and economic reform and of moral and spiritual renewal should be obvious by now to even the most unimaginative positivist. If it is not, it is because he or she is unimaginative, not because he is a positivist.

Epistemology has no political or moral consequences. The source of morality is sympathy, the habit of experiencing the joys and sufferings of others as, in some measure, one's own. The wider and deeper our sympathies - the more people whose joys and sufferings we can imagine, and the more keenly those joys and sufferings affect us - the more moral we will be, whatever our beliefs about knowledge, truth, meaning, agency, or the nature of the good. This is why great philosophers can have banal or even (like Plato and Heidegger) repugnant political views, and why philosophical duffers like Camus can be moral heroes. It is, I believe, what the late Richard Rorty meant by giving his late essays titles like "The Priority of Democracy to Philosophy" and "Take Care of Freedom, and Truth Will Take Care of Itself." Philosophy makes nothing happen; for better or worse, it leaves the world as it finds it - sometimes a little bit less confused, but just as often a little more.