Consilience
The unity of knowledge and the reunification of learning
If a single ambition unified Edward O. Wilson's astonishingly varied career — the ants and the islands, the theory of sociobiology and the defense of biodiversity — it was the conviction that all knowledge is ultimately one. He gave that conviction its fullest and most systematic expression in Consilience: The Unity of Knowledge (1998), a book that reached beyond biology to argue for the reunification of the sciences with the social sciences, the humanities, and even ethics and religion, under a single web of cause and effect. Consilience was Wilson's intellectual testament, the work in which the synthesizing impulse that had driven his whole life became an explicit philosophical program: the claim that the great branches of learning, long divided into hostile and mutually unintelligible camps, could and should be joined into a single coherent understanding of the world and of humanity's place within it. This chapter examines that program — its ancient roots in the dream of unified knowledge, its Enlightenment ancestry, its proposed bridges across the great divisions of the intellect, and the fierce debates it provoked. The philosophical foundations of consilience within biology itself — reductionism, emergence, the central position of biology — are treated in Chapter 13; here the subject is the grand cross-disciplinary program that Wilson built upon those foundations.
Wilson traced the dream of unified knowledge to its origin in the ancient world, in what he called the Ionian Enchantment — the conviction, first articulated by Thales of Miletus and the other Ionian philosophers of ancient Greece, that the bewildering diversity of the world can be reduced to a small number of underlying natural laws. This ancient Greek intuition that the universe is orderly and can be explained by a few principles was, for Wilson, the founding faith of all natural science, the deep assumption on which the entire scientific enterprise rests. He recounted his own youthful experience of the Enchantment, the moment as a young student when he first glimpsed the possibility that all of nature might be understood as a single connected system, and he confessed that this vision had animated his work ever since. For the actual term consilience, Wilson reached back to the nineteenth-century polymath William Whewell, who had coined it to describe the jumping together of knowledge — the moment when facts and theories from different fields leap together to reveal a common explanation, when independent lines of evidence converge on the same underlying truth. Consilience, in this sense, was not merely the hope of unity but its demonstration: the repeated experience, across the history of science, of separate disciplines discovering that they were describing the same reality from different angles.
Wilson was frank about both the promise and the difficulty of the enterprise. The promise was immense: he held out the prospect that unifying knowledge would vastly increase humanity's power to understand and manage itself and its world, giving us, for the first time, a comprehensive grasp of our own nature and situation. To see the connections among all the branches of learning, to trace the thread of cause and effect from physics through biology to the workings of the human mind and the forms of human culture, would be to command an understanding no fragmented knowledge could supply. But the obstacles were equally formidable, and Wilson did not minimize them. The complexity of human phenomena — the mind, culture, society — is so vast that the consilient chains connecting them to their biological foundations are extraordinarily difficult to trace, and may in places be beyond the reach of any foreseeable science. Consilience proceeds, he argued, by following chains of cause and effect that cross the boundaries between disciplines, and where those chains grow too tangled to follow, the program stalls. Wilson presented consilience not as an accomplished fact but as a working hypothesis and a research program — a faith, grounded in the past success of science, that the connections exist and can in time be found.
The whole enterprise, Wilson freely acknowledged, was a biologist's vision of unified knowledge, and it bore the marks of its origin. It was as a biologist that he had come to see the living world as a single connected system, and it was from biology that he drew both his method and his confidence. This gave his program a distinctive shape, for Wilson assigned biology a special and central place in the unification of knowledge. Biology, he argued, occupies the crucial middle ground between the physical sciences below and the social sciences and humanities above — connected downward to chemistry and physics through the molecular machinery of life, and upward to psychology and culture through the evolved human mind. Precisely because it straddles this boundary, biology was for Wilson the natural bridge across which the consilient program must pass, the discipline through which the exact sciences reach toward the human ones. The centrality of biology to consilience was more than a professional prejudice; it followed from the fact that human beings are biological creatures, so that any attempt to connect the sciences to the study of humanity must run through the biology of the human organism and its evolved mind (the special standing of biology is examined further in Chapter 13).
The method by which science had achieved its consilient successes was, Wilson argued, reductionism — the strategy of breaking complex phenomena down into their component parts to understand how they work. Reductionism, he insisted, is the chief and most powerful tool of the natural sciences, the analytic blade that had cut through the complexity of nature to reveal the simple laws beneath. But Wilson was careful to pair reduction with its complement, synthesis: science proceeds not only by taking nature apart but by putting it back together, by showing how the higher-level phenomena of the world emerge from the interactions of their lower-level parts. The two movements — reduction downward to the elementary components, synthesis upward to the emergent wholes — are the twin engines of scientific understanding, and consilience depends on both. This balanced view mattered to Wilson's larger argument, for his critics would accuse him of a crude reductionism that dissolved everything into physics; his actual position was that reduction and synthesis together trace the connections between levels of organization, and that consilience means understanding how each level arises from and connects to the others, not abolishing the higher levels in favor of the lower (this philosophical machinery is developed in Chapter 13).
Against this account of science's power, Wilson set a lament: the fragmentation of knowledge into isolated disciplines that no longer speak to one another. The great branches of learning — the natural sciences, the social sciences, the humanities — had drifted so far apart, he argued, that scholars in different fields could no longer understand one another, each speaking a private language and pursuing questions the others found unintelligible. He revisited C. P. Snow's famous diagnosis of the two cultures — the mutual incomprehension between the scientific and literary intellectuals — and argued that the divide had only deepened since Snow named it, fracturing further into countless specialized subcultures. This fragmentation Wilson regarded as a genuine intellectual catastrophe, not merely an inconvenience: a world in which knowledge is broken into disconnected fragments is a world in which no one can grasp the connected nature of reality, and in which the great problems of human existence — problems that cut across every disciplinary boundary — cannot be adequately addressed. The reunification of knowledge was therefore, for Wilson, not an academic tidiness but an urgent necessity, a precondition for humanity's capacity to understand and govern itself.
Wilson placed his own project in a long historical lineage, presenting Consilience as the renewal of an ambition that had flourished once before and then been lost: the dream of the Enlightenment. The Enlightenment thinkers of the seventeenth and eighteenth centuries, he recounted, had entertained a grand ambition to unify all knowledge through reason, to bring every domain of human understanding under a single rational scheme. He celebrated Francis Bacon as a founding prophet of this vision, the herald of an empirically grounded knowledge that would master nature for human benefit, and he recounted the great effort of the French Encyclopedists to gather and systematize the whole of human learning into a single ordered compendium. The Enlightenment faith that reason could comprehend nature and drive human progress was, for Wilson, one of the noblest aspirations in the history of thought — and its gradual dissolution, one of the most consequential losses. He traced how that vision had faded, undermined by the sheer growth and specialization of knowledge and by the reaction against it.
At the heart of the Enlightenment vision, as Wilson recounted it, lay a soaring confidence in the power of reason — the faith that human reason, systematically applied, could master nature and drive an open-ended progress of the human condition. The philosophes of the eighteenth century believed that the same rational methods which were unlocking the secrets of the physical world could be turned upon human society, upon government and morality and the mind itself, to produce a comprehensive and cumulative understanding that would liberate humanity from ignorance and superstition. This was the ambition Wilson sought to revive: not merely the unification of the sciences among themselves, but the extension of scientific understanding to the whole of human concern, in the confidence that reason could there too find order and law. He recognized that the Enlightenment's optimism had come to seem excessive, even dangerous, to later generations chastened by the catastrophes of modern history; but he insisted that its central conviction — that the world is intelligible and that reason can comprehend it — remained sound, and that the failures attributed to the Enlightenment were failures to complete its project rather than consequences of pursuing it. The task, as he saw it, was to take up the unfinished Enlightenment ambition again, armed now with the vastly greater knowledge that two further centuries of science had accumulated.
The reaction Wilson had chiefly in mind was Romanticism — the powerful counter-movement that arose against Enlightenment rationalism, exalting emotion, intuition, individual genius, and the irreducible mystery of human experience over the cool analytic ambitions of reason. The Romantic reaction, in Wilson's telling, had deflected the Enlightenment project, insisting that the deepest human realities — art, love, the soul, the sublime — lay forever beyond the reach of scientific explanation, and thereby helping to sunder the sciences from the humanities. Wilson treated Romanticism with a certain respect, acknowledging the truths it defended about the richness of human experience, but he regarded its central claim — that the humanities occupy a domain permanently closed to science — as mistaken, and as the source of the unhappy division he sought to heal. The Enlightenment vision of unified knowledge, he argued, had dissolved amid this Romantic reaction and the accelerating specialization of the disciplines, until the grand ambition to comprehend everything within a single scheme came to seem naive or even hubristic. Yet the vision had never entirely died: the natural sciences, Wilson argued, had quietly carried the Enlightenment torch forward, continuing to unify their own domains through consilient explanation even as the broader project faltered, and it was on the proven success of the natural sciences that he proposed to revive the larger ambition.
That proven success was, for Wilson, the ground of his confidence. The natural sciences, and physics above all, he presented as the supreme example of consilience in action — a vast, interlocking body of knowledge in which the phenomena of one level are explained by the laws of the level below. He traced the consilient chain that connects physics to chemistry and chemistry to biology, each field grounded in and continuous with the one beneath it, the whole forming an unbroken ladder of explanation from the elementary particles to the living cell. The power of this achievement, Wilson argued, lay in the capacity of natural laws to compress enormous complexity into simple, predictive statements, and in the guiding role of theory, which organizes observation and reveals the deep connections among superficially disparate phenomena. From this extraordinary record of success Wilson drew confidence for his broader project: if the natural sciences had achieved such consilience among themselves, and had already extended their reach downward from biology toward chemistry and physics, then there was no principled reason the same consilient method could not be extended upward and outward, into the study of mind, culture, and society. The study of the human being, he proposed, was simply the next frontier for a consilient science that had already conquered the physical world.
To picture the path from the physical sciences to the human world, Wilson reached for a myth: Ariadne's thread, the strand that guided Theseus safely through the labyrinth of the Minotaur. Consilience, he suggested, requires a continuous thread of explanation running through the labyrinth of nature's levels — an unbroken chain connecting atoms to molecules, molecules to cells, cells to organisms, organisms to minds, and minds to cultures. The crucial junction along this thread, the point where the natural sciences meet the social sciences and the humanities, was for Wilson the human brain: it is in the biology of the brain that mind arises from matter, and therefore in the science of the brain that the great divide between the sciences and the humanities can at last be bridged. He pointed to the emerging sciences of complexity, which seek to explain how order and higher-level pattern arise from the interactions of many simpler parts, as a promising means of following the thread upward through the difficult transitions. And he argued that the most fertile frontiers of contemporary knowledge now lie precisely between the established disciplines, in the borderlands where fields meet — for it is there, at the junctions, that the connecting thread of consilience must be traced. Beneath all the bewildering complexity of the world, Wilson maintained, lies a fundamental unity, and Ariadne's thread was his guiding image for the enterprise of finding it.
The thread's power, Wilson emphasized, lay in the continuity of explanation it promised — a chain that in principle connects atoms to molecules, molecules to cells, cells to tissues and organs, organs to organisms, and organisms to the minds and societies they compose, with no gap at which the connection is broken. At each level, new and emergent properties appear that were not present at the level below; but emergence, in Wilson's account, does not sever the levels from one another. The higher properties arise from the interactions of the lower-level parts and remain, in principle, explicable in terms of them, even where the explanation is too complex to trace in practice. This was the crux of his answer to those who held that mind, or culture, or moral value, constitutes a realm forever closed to natural science: there is no point along Ariadne's thread, he insisted, at which nature hands off to something outside itself, no level at which a new and non-natural principle must be invoked. The apparent discontinuities — between matter and life, between brain and mind, between biology and culture — are not breaks in the causal fabric but merely the places where the connecting explanations are hardest to trace, the difficult passages of the labyrinth through which the thread must be patiently followed. The unity of knowledge, for Wilson, was ultimately a claim about the unity of nature itself: because the world is one connected causal system, the knowledge that describes it can and should be one as well.
The first and most fundamental of the bridges Wilson proposed to build was the bridge from brain to mind. The mind, he argued, is the product of the physical brain, its every process ultimately explicable in biological terms — a position of thoroughgoing materialism that placed the study of mind squarely within the consilient chain of the natural sciences. He surveyed the advances of neuroscience that were beginning, in his lifetime, to trace thought, emotion, and perception to the physical operations of neural tissue, and he addressed even the hard problem of consciousness, expressing confidence that subjective experience would ultimately yield to biological understanding rather than remaining forever a mystery. The mind, in his account, is a suite of evolved adaptations shaped by natural selection; emotion and reason are intertwined in its workings; memory and even the sense of a unified self are constructions of the brain, useful devices assembled by evolution rather than glimpses of some immaterial soul (this psychology is developed in Chapter 18). A genuine science of mind, uniting neuroscience, psychology, and evolutionary biology, was for Wilson both an achievable goal and the indispensable keystone of the whole consilient arch, since it is through the mind that every higher human phenomenon — culture, society, art, morality — ultimately arises.
From the brain, the thread ran onward to culture, and here Wilson placed the concept he regarded as the crucial link in the whole chain: gene-culture coevolution. The central problem of a consilient human science, he argued, is to explain how genes give rise to culture — how the biological inheritance encoded in our DNA produces the vast and varied phenomenon of human cultural life. His answer lay in the epigenetic rules, the inherited biases in perception, cognition, and emotion that channel cultural development along certain paths rather than others, so that culture, however diverse, is held on what he famously called a genetic leash (the mechanism is treated in Chapter 14). Genes and culture, in this account, have evolved together across the long history of the species, each shaping the other in a continuous coevolutionary circuit, and a universal human nature — the ensemble of evolved epigenetic rules and behavioral predispositions common to all people — filters and biases the cultures that human beings construct. Gene-culture coevolution was, for Wilson, the bridge that finally joins the natural sciences to the study of human culture, the theoretical link that makes a consilient human science possible by connecting the genetic and the cultural in a single explanatory framework.
At the center of this bridge stood human nature itself, which Wilson defined as the ensemble of evolved epigenetic rules and human universals — the recurring features found in every known human society, from kinship systems and incest taboos to the moral sentiments of sympathy and fairness. These universals, he argued, are evidence of a shared human nature shaped by natural selection during the long prehistory of hunter-gatherer life, when the essential features of the human mind were forged in adaptation to that ancestral environment. Human nature, so understood, is neither infinitely malleable nor rigidly determining: it constrains and biases human behavior without wholly dictating it, setting the boundaries within which the diversity of cultures unfolds. Wilson warned pointedly against the opposite error — the blank-slate assumption that the mind has no evolved structure and that human behavior is shaped entirely by culture and environment — arguing that ignoring human nature leads to failed social theories and misguided policies built on a false picture of what human beings are (the general account of human nature is developed in Chapter 16). Human nature, in his consilient scheme, is the indispensable foundation, the bedrock on which any true understanding of society, culture, and morality must be built.
Wilson grounded this claim in the evidence of human universals — the features that recur across every known human society, however different in surface detail. The anthropological record, he argued, reveals a common substrate beneath the diversity of cultures: kinship classifications, incest avoidance, the division of labor, status-seeking, gift exchange, marriage customs, religious belief, aesthetic expression, and much else appear in every society ever studied, precisely because they flow from a shared and evolved human nature. Among the most important of these universals, for Wilson's argument, were the innate moral sentiments — the dispositions toward sympathy, fairness, gratitude, and indignation that underlie human ethical life everywhere, and the evolved tendencies toward kin favoritism and reciprocal cooperation that structure human social relations across all cultures. These were not, in his account, arbitrary cultural conventions but the predictable expressions of a nature shaped by natural selection during the long hunter-gatherer past. Yet Wilson was careful to insist that this evolved nature constrains without wholly determining: human beings are not puppets of their genes but creatures whose inherited predispositions set the boundaries and biases within which an immense cultural creativity operates. Human nature, in his formula, holds culture on a leash — a leash long enough to permit vast variation, but not so long as to allow culture to escape the gravitational pull of the evolved mind entirely.
Armed with this account of human nature, Wilson turned to the social sciences, and offered a pointed and unsparing critique. The social sciences, he argued, had drifted into fragmentation and incoherence, cut off from the biological foundations that alone could give them explanatory power, each discipline pursuing its own methods and models in isolation from the others and from the natural sciences beneath them. Economics he criticized for relying on unrealistic models of human behavior — the fiction of a perfectly rational, self-interested agent — detached from the actual evolved psychology of real human beings. Anthropology, by contrast, he identified as the social science best positioned to connect biology and culture, straddling as it does the boundary between the natural and the human. The remedy, in every case, was the same: the social sciences must be grounded in biology, psychology, and evolutionary theory, must recognize that culture itself is a biological phenomenon produced by evolved minds, and must thereby gain the predictive and explanatory power they had so conspicuously lacked. Wilson envisioned a unified human science that would join the social sciences to biology and psychology, dissolving the artificial barriers between them and grounding the study of human affairs in a realistic understanding of human nature.
The gap between the social sciences and biology, Wilson argued, was rooted in history rather than in any real discontinuity in nature. The social sciences had grown up in the long shadow of the assumption that human beings stand apart from the rest of the living world, that culture floats free of biology, and that the study of human affairs therefore requires methods and principles entirely its own. This separation, Wilson contended, had cost the social sciences dearly, leaving them fragmented, quarrelsome, and comparatively weak in the predictive and explanatory power that marks the mature natural sciences. A social science grounded in biology, psychology, and evolution would, he predicted, gain genuine explanatory force — the ability not merely to describe human behavior but to explain why it takes the forms it does, and even, within limits, to predict it. Culture itself, he insisted, is a biological phenomenon, produced by evolved minds interacting under particular conditions, and there is no reason in principle why it should not be studied with the same consilient methods that had illuminated every other level of nature. Wilson's vision of a unified human science was not a proposal to abolish the social sciences but to complete them, to supply the biological foundations they had long lacked and thereby to raise them to the explanatory power their subject deserved.
If the extension of consilience to the social sciences was provocative, its extension to the arts was more provocative still — yet Wilson pressed it with conviction and, notably, with care. The arts, he argued, arise from and appeal to evolved features of human nature: the aesthetic preferences that shape our responses to art are grounded in epigenetic rules, in the evolved biases of the human mind toward certain forms, colors, patterns, and narratives. The arts move us, he proposed, precisely because they engage the evolved emotional and cognitive machinery of the brain, striking the deep chords of a human nature shaped by natural selection; and the recurring universals of art across human traditions are evidence of that shared underlying nature. Wilson proposed that scientific knowledge of the mind could enrich the interpretation of the arts, illuminating why particular works move us as they do and what in our evolved constitution they engage. But he was emphatic on the point his critics most feared: that a biological understanding of the arts enriches rather than diminishes them, deepening our appreciation rather than explaining it away. Linking the arts to the biology of the mind, he argued, was the way to bridge the divide between the sciences and the humanities — not by reducing the one to the other, but by revealing the common human nature from which both spring (this program continues in the treatment of creativity in Chapter 24).
Wilson developed the biological account of the arts with some care, aware that here more than anywhere he risked the charge of philistine reductionism. Aesthetic preferences, he argued, are not wholly arbitrary or purely cultural but rest in part on evolved epigenetic rules — inherited biases toward certain proportions, rhythms, colors, and forms that recur across human artistic traditions and that trace to the deep structure of human perception. The arts function, in his account, as a form of communication, a means of transmitting emotion and experience from one mind to another through symbols that engage our shared evolved responses; this is why a poem or a painting or a piece of music can move a stranger across the barriers of language and time, striking chords that all human beings possess. The recurring universals of art — the near-ubiquity of music, of narrative, of rhythmic and representational forms — were for Wilson further evidence of the common human nature underlying all cultural expression. But he returned insistently to the point his humanist critics most doubted: that to understand the biological roots of art is to enrich our appreciation of it, not to diminish it. Knowing why a sunset or a symphony moves us, he argued, adds a further dimension of wonder rather than dispelling the wonder we already feel; the scientific and the aesthetic responses are not rivals but complements, and the fear that explanation must destroy beauty is, in his view, simply mistaken.
The most contested extension of all was to ethics and religion, where Wilson advanced the boldest and most disputed claims of the entire book. Ethics, he argued, originates not in divine command or transcendent moral truth but in the evolved moral sentiments of human nature — the dispositions toward sympathy, fairness, reciprocity, and kin loyalty that natural selection had built into the human mind. He framed the deepest question in ethics as a choice between two opposed views: transcendentalism, the belief that moral principles exist independently of humanity, whether in the mind of God or in some Platonic realm of eternal truths; and empiricism, the view that ethics is a product of human nature and evolution, to be understood through science like any other natural phenomenon. Wilson placed himself firmly on the empiricist side, arguing that a scientifically grounded ethics could guide human conduct without appeal to religion, and that grounding morality in human nature makes it more secure, not less, by tying it to the actual constitution of the beings whose conduct it governs (the ethical argument is developed in Chapter 22). Religion, too, he brought within the consilient scheme, analyzing it as a product of evolution arising from the human predispositions toward group belonging and the search for meaning, and explaining its extraordinary persistence by the evolved emotional needs it satisfies rather than by the truth of its doctrines (religion is treated in Chapter 23).
The distinction between empiricism and transcendentalism was, for Wilson, the pivotal fork in the whole theory of ethics, and he framed it with characteristic sharpness. The transcendentalist holds that moral principles have an existence independent of the human mind — that they are woven into the fabric of the universe, or issue from the will of God, and that human beings discover rather than invent them. The empiricist, by contrast, holds that moral principles are products of the human mind, evolved through natural selection because they promoted survival and cooperation among our ancestors, and that they are therefore to be understood, like everything else about human beings, through the natural sciences. Nearly every ethical and religious tradition, Wilson observed, is transcendentalist at its core, resting the authority of its moral commands on some source beyond humanity; his own empiricism represented a radical alternative, locating the origin and authority of morality within human nature itself. He was well aware of the objection that an evolved morality might seem to lose its binding force — that if our moral sentiments are merely adaptations, we might feel free to disregard them. But Wilson argued the reverse: that understanding morality's real origins, far from dissolving it, allows us to examine our moral intuitions critically, to distinguish those that still serve us from those that were adaptive in the ancestral past but are destructive now, and thereby to build an ethics more rational and more humane than blind obedience to inherited or revealed commands could ever produce.
Wilson was candid that this naturalizing of ethics and religion represented the frontier where consilience was most vulnerable and most fiercely resisted. To claim that morality is a product of evolution rather than of transcendent truth, and that religion is a natural phenomenon to be explained rather than a revelation to be believed, was to challenge convictions held sacred by much of humanity, and Wilson knew his empiricist worldview would strike many as a diminishment of the things they held most dear. He did not soften the challenge, advocating frankly for a naturalistic worldview in which ethics and religion alike are understood as products of human nature and evolution. Yet he insisted that this worldview need not be bleak or corrosive: a morality grounded in human nature, he argued, could be as binding and as inspiring as one grounded in divine command, and perhaps more so, because it rested on the real and shared constitution of humanity rather than on contested metaphysical claims. Whether Wilson's empiricist ethics can in fact bear the weight he placed on it remains a genuine and unresolved philosophical question, one his critics pressed hard and one this reader takes up more fully in Chapter 22; here it is enough to note that Wilson advanced the claim as the culminating and most demanding application of his consilient program.
To what end, finally, should all this unified knowledge be directed? Wilson closed Consilience by insisting that the unification of knowledge was not an end in itself but a means to human survival and flourishing. The great crises confronting humanity — above all the environmental crisis and the accelerating loss of biodiversity — are, he argued, interlocking problems that cut across every disciplinary boundary, and they cannot be understood, let alone solved, by a fragmented knowledge in which no one can grasp the connected nature of reality. Only unified knowledge, joining the insights of the natural sciences, the social sciences, and the humanities, can give humanity the comprehensive understanding it needs to navigate the dangers of its own unprecedented power. Wilson warned that fragmented knowledge leaves humanity unable to see the whole, and therefore unable to act wisely in a moment when its choices will determine the fate of life on Earth. He advocated what he called existential conservatism — the preservation of both human nature and the living world, the two irreplaceable inheritances on which any tolerable human future depends. And he closed, as he so often did, on a note of hope: the conviction that unified knowledge could help humanity flourish while preserving the rest of life, and the reaffirmation of his lifelong faith that all knowledge is, at bottom, one.
The urgency of this closing argument distinguished Consilience from a merely academic exercise in the philosophy of knowledge. Wilson believed that the fragmentation of the intellect had become genuinely dangerous — that a humanity which could not see its situation whole, whose knowledge was scattered among specialists who could not speak to one another, was a humanity poorly equipped to survive the crises its own power had created. The great problems of the age — environmental collapse, the loss of biodiversity, the management of technologies that now touch human nature itself — do not respect the boundaries between disciplines; they are at once biological and economic, technological and ethical, scientific and cultural, and they can be grasped only by a knowledge capable of crossing those boundaries. Wilson's existential conservatism — the resolve to preserve both the evolved human nature and the living biosphere that are humanity's two irreplaceable inheritances — followed directly from this diagnosis: only a species that understood itself and its world as connected wholes could hope to make the wise choices on which its future depended. Consilience, in the end, was not offered as an intellectual luxury but as a practical necessity, the kind of unified understanding without which, Wilson feared, humanity would blunder through the coming bottleneck half-blind, unable to comprehend the connected nature of the very predicament it faced.
Consilience was the boldest expression of the vision that had animated Wilson's entire career, and also the most controversial. To its admirers, it was a magnificent and necessary call to heal the fractures of the intellect, to restore the lost unity of knowledge, and to bring the full power of science to bear on the largest questions of human existence. To its critics, it was an overreaching act of intellectual imperialism, an attempt to annex the humanities and social sciences to biology and to reduce the richest achievements of human culture to evolutionary mechanism. The truth, as Wilson would have insisted, lies in the testing: consilience is a hypothesis about the ultimate unity of knowledge, and its vindication or refutation lies in whether the bridges he proposed can actually be built, whether the thread of explanation can in fact be traced unbroken from the atom to the work of art. What is beyond dispute is the grandeur of the ambition and the seriousness with which Wilson pursued it. In an age of ever-narrowing specialization, he dared to insist that knowledge is one, that the sciences and the humanities describe a single reality, and that humanity's future may depend on its willingness to see that reality whole. Whether or not the full program of consilience is ever achieved, the vision it embodies — of a unified understanding adequate to the largest questions of human existence — remains one of the noblest aspirations in the history of thought, and the fullest statement of what Edward Wilson believed the life of the mind was ultimately for.