Nature © Macmillan Publishers Ltd 1998

8Consilience: The Unity ofKnowledgeby E. O. WilsonKnopf: 1998. Pp. 322. $26

Paul H. Harvey

It was 1975. John Maynard Smith burst intomy room. He had looked at E. O. Wilson’snew book, the now infamous Sociobiology,and exclaimed that every Marxist in theWestern world would be outraged by it. May-nard Smith was right, although the extent towhich Wilson had anticipated the kerfufflehas never been clear.

Six major books on, Wilson brings usConsilience. Its first thesis is that the humani-ties, sociology, religion, ethics, art apprecia-tion and almost everything else outside thecurrent remit of science that has not found itsanalytical roots in evolutionary biology willsoon do so. Its second thesis is that, once weunderstand how we came to be, we shall beconstrained in determining where to go.Does this mean Wilson has failed to rehabili-tate himself? The answer is no. The book ismarked by a scientific rigour found wantingby many in his earlier works. Every step of theway he questions his assumptions, methodsand tentative conclusions. Thankfully, he hasnot changed his vision, except by expandingits horizons.

Wilson makes a formidable argument forconsilience — unifying on the basis of a com-mon theoretical framework — of those near-disciplines that have no rational structure.The central concept underlying the book isthe epigenetic rule: the idea that, because ofour genetic make-up and the environment inwhich we develop, each individual has biasestowards making certain behavioural de-cisions rather than others. If we can establishwhat those biases are and begin to under-stand their molecular and physiologicalcauses, we shall be able to understand why webehave as we do. It is a massively tall order,and in terms of getting to grips with epige-netic rules, my own impression is that wehave not advanced markedly in the pastdecade or so. Wilson still uses the examplesof colour vision and incest avoidance, theempirical bulwarks of his co-authored bookGenes, Mind, and Culture from 17 years ago.

But we have come a long way in under-standing the functional analysis of behav-iour, development and neurobiology. Thebook charts a marvellous path through theimportant empirical findings in these disci-plines, placed in a framework for under-standing and revealing tasks for the futurethat is a model of popular science writing. Italso provides the strongest evidence yet forWilson as a successful visionary. Sociobiologywas an agenda as well as a review, and one

that has been largely realized. True, he gotsome parts wrong: his claim for the impor-tance of trait group selection, for example.But most of it was right: evolutionary-basedbiological anthropology has emerged andeven started to mature. He was not to knowthat molecular genetics would develop as ithas, but its daily discoveries provide grist forhis mill.

But in his new book, when discussingethics, religion, sociology or art apprecia-tion, he is forced to epigenetic rules viewedhazily, as through a fog (not one of his ownmaking; that is the state of the art). The con-cepts are clear; if we could just summon therules, we should reveal the proper founda-tions for the subjects. There is a long way togo, but we can afford to be patient becausethere is no competition. A proper under-standing of these subjects will simply have towait until we understand our own predispo-sitions and the reasons for them.

In art, the few glimmers afforded by PietMondrian’s spaced trees or the golden sec-tion point towards the rules but they cannotyet describe them, let alone trace their neuralcausations. (Nature’s weekly art and sciencearticle is exactly what we need if we are tokeep ourselves abreast of the challenge.)There are beautifully written patches of fluo-

rescent prose in Wilson’s treatment of thesesubjects. He treasures apparent insights intoPalaeolithic times and minds when the cul-tural changes occurred that produced us. Hedescribes what he imagines are moments inthe lives of our ancestors, often gleaned fromdays in the life of contemporary bushmen.

He is now the first to admit the ‘just-so’nature of his tall tales, but we all have to startsomewhere. It is getting a start that matters.There is no one way to proceed in science;one just has to go at it from whatever pinholeof opportunity presents itself, thinkingaround and around a subject until a way in isfound. This view of the scientific enterprise iswell known to evolutionary biologists andecologists because they, like astronomers,often deal with the outcome of historicalprocesses. They try to unravel history with-out an evident written record; in biology thefossil record can provide occasional guide-lines for some problems, just as looking lightyears into the past can help astronomers.

The second theme of the book may stillupset the die-hards. Wilson remains a deter-minist in an important sense. He believesthat the epigenetic rules are sufficientlyhardwired that our environment of choice isitself largely predetermined. We are contentto behave only in certain ways and to live in

NATURE | VOL 392 | 2 APRIL 1998 451

Further steps towards one culturespring books

Reaching out: Wilson proposes that many disciplines will find analytical roots in evolutionary biology.

AP

Nature © Macmillan Publishers Ltd 1998

8

certain sorts of societies. A scientist wants toknow why, but for the politician and theeconomist this limits courses of action.There will, of course, be alternatives avail-able, but in Wilson’s world they are apprecia-bly more restricted than is generally thought.Economists do not appreciate the optionsbecause they have yet to think of them.

Wilson is a kind man, but he has no prob-lems producing withering denouncementswhere they are called for. His description ofour ecological plight, and his heartfelt pleafor understanding and urgent action, arewritten with such authority, clarity and pas-sion that I have read nothing to touch them.Nobel laureates in economics who fail toappreciate the world’s finite resources andwho argue for our wants in the short termrather than our needs for a sustained futureare targets in this book. Evolutionary psy-chologists also get a timely warning. I wasdelighted to see one of their gurus pointingout so very dispassionately that, althoughDarwinian explanations abound, the theoryis in its infancy and the database againstwhich ideas are being tested remains poor.

Within this second theme, Wilson is atpains to circumscribe his own limits.Returning to art, he writes: “While biologyhas an important part to play in scholarlycriticism, the creative arts themselves cannever be locked in by this or any other disci-pline of science.... Works of art communicatefeeling directly from mind to mind, with nointent to explain why the impact occurs. Inthis defining quality, the arts are the anti-thesis of science.”

Wilson has had such a broad agendathrough his career that he has frequentlysought the advice of others for complemen-tary expertise. For some of his researchmonographs he has collaborated with co-authors. At one end of the axis of excellencewas Robert MacArthur. Fortunately, likeGeorge Oster, most of Wilson’s collaboratorslie close to MacArthur in this respect. And aswith Sociobiology, so with Consilience — thevision is Wilson’s but much of the detailedunderstanding of mechanism is necessarilygleaned from experts in their own fields. Theresponses from those working in the areas towhich the clarion calls are directed maydepend on how well Wilson has chosen hisexamples, and how accurately he hasdescribed the state of their art.

His own pool of knowledge and grasp ofcontemporary advances is astonishing, buteven so we can expect the nitpickers togather. I hope they will take time to evaluatethe broader canvas and, where necessary,supply their own case studies in mountingwhatever responses this monumental workdemands. In any event, it is time to get onwith the job. If we have to go through abruising session like that following Socio-biology, I think that this time most evolu-tionary biologists will stand behind Wilson,

albeit obliquely. He deserves no less.Some will argue that to bring evolution-

ary biology and the associated epigeneticrules into such areas as art appreciation willturn us into Philistines. They should bedirected to Darwin’s response to the evolu-tionary interpretation for life itself in the lastparagraph of Origin of Species. The grandeurin his view of life provided us with a newdimension for appreciating the naturalworld but removed none of the old. Or, asWilson might have it, our biophilia wasintensified.Paul H. Harvey is in the Department of Zoology,University of Oxford, South Parks Road, OxfordOX1 3PS, UK.

At the limitImpossibilityby John D. BarrowOxford University Press: 1998. Pp. 279.£18.99, $25

John L. Casti

To those enamoured of the belief that thehuman spirit knows no bounds or limita-tions, a tour of twentieth-century sciencemust be a rather depressing experience. Ifthere is any common denominator runningthrough the scientific breakthroughs of ourage it is the idea that there are limits.

Starting with Einstein’s speed limit of theUniverse in a ray of light and Heisenberg’slimits on what can be measured with cer-tainty, through Gödel’s limits on what can beknown by following a set of rules and on toArrow’s famous result about the impossibi-lity of a perfect democratic society, the his-tory of modern science is riddled with logicaland physical limits of all sorts.

In this illuminating, well-written accountof Limits (with a capital L), John D. Barrowchronicles and explains the limits of scienceas a reality-generation mechanism — andwhy it matters.

As he carefully points out, limits to theability of science to answer a given questionabout the world as we see it come in all sizesand shapes. There are political and ethicallimits on how much latitude a society is will-ing to give to investigators to answer a ques-tion. There are practical limits on theamount of time or energy or money that canbe spent in answering a question. And, fi-nally, there are logical limits.

Although Barrow pays more than lip ser-vice to the former sorts of limitations onour ability to tease out the ‘scheme ofthings’, it’s clear that his real focus is on logi-cal limits. Rightly so, too, because ultimate-ly these are the limits that count — at leastfor the scientist and scholar, if not thepolitician and social agitator. When one islooking for a needle in a haystack, it’s ofmore than passing interest to know that a

needle is really there to be found. As Barrow points out, all the scientific

knowledge we have about nature comesfrom models that we create of natural phe-nomena. These models, in turn, are almostalways mathematical in character. It followsthen that it’s only a small approximation tosay that the issue of logical limits to sciencecomes down to the limits of computation, asany mathematical model can be regarded asan algorithm for processing inputs (thestatement of the question and its circum-stances) into an output (the answer).

This notion of scientific knowledge raisesseveral fundamental questions. How doesthe mathematical model relate to the real-world phenomenon it purports to represent?Does the Turing-machine model of compu-tation impose intrinsic limits on what we canknow? What is the relationship between thecomputational powers of the human brainand those of our computing machines?

One question missing from the list —and the book — arises from the assumptionthat our models of nature must necessarilybe mathematical. This question is: is there analternative to a mathematical formulation ofa model of natural phenomena?

The difficulty here is that one is leftperched on the horns of a dilemma. Eitheryou use the mathematical representation ofthe question of concern, and then try to jus-tify why mathematical insolubility impliesthe same for the model’s real-world corre-late. Or you forsake mathematics altogether,and then face the difficulty of trying to createa convincing real-world substitute for themathematical notion of proof, in order toproduce a knockdown argument for why the question of concern is logically un-answerable. Impossibility evades this dilem-ma simply by ignoring the non-mathemati-cal alternative.

But no matter. Taken on a whirlwind tourof the mind, Gödel’s theorem, quantum the-ory, free will, voting paradoxes, time travel,computational intractability, sandpile mod-els, the topology of space, nanotechnology,the forces of nature, the evolution of the Uni-verse, complexity science, computer chess-playing, percolation theory, human con-sciousness, economic forecasting, blackholes, the Brouwer fixed-point theorem,artificial intelligence and the Heisenberguncertainty principle, one can only wonderhow Barrow can possibly make all thesethings fit together into a coherent storyabout the limits to science. Well, contrary toall expectations, he does make them fit —and in only 250 pages!

So for about as good an account as you’regoing to get of where science stops, read thisbook. It won’t tell you any final answer. Butthe journey is far more interesting — andimportant — than the destination.John L. Casti is at the Santa Fe Institute,1399 HydePark Road, Santa Fe, New Mexico 87501, USA.

spring books

452 NATURE | VOL 392 | 2 APRIL 1998