As any comic knows, timing is crucial. Of course, good material is basic, but timing builds suspense, offers surprise, puts the focus on the punch line, brings out the hidden meaning. The delights of serendipity also come largely from timing. It is not just the happy accident but the unexpected discovery that comes precisely at the moment when it is needed, the chance juxtaposition that brings out the potential in a given context. The beneficiary of serendipity looks smart as wellˇand not wrongly. As Pasteur said, chance favors prepared minds. But as Robert Merton and Elinor Barber show, chance is also socially organized, and certain contexts favor both the novel observation and the capacity to make it matterˇa mostly theoretical capacity in the case of science, where, it turns out, serendipity matters a lot.

The word "serendipity" was coined in 1754 by Horace Walpole. An English aristocrat remembered for his witty and elegant correspondence, Walpole wrote to his distant cousin Horace Mann that he was known among his friends as the beneficiary of a special sort of luck: "I find everything I want . . . wherever I dip for it." A collector of bric-a-brac and books and an enthusiast for obscure heraldry, Walpole "dipped" often. What was crucial, he suggests, was how insight, information, and collectible objects turned up seemingly of their own while he was looking for something else. His primary example was a "silly fairy tale" in which "three Princes of Serendip" made discoveries "by accidents and sagacity, of things which they were not in quest of: for instance, one of them discovered that a mule blind of the right eye had travelled the same road lately, because the grass was eaten only on the left side, where it was worse than on the rightˇnow do you understand Serendipity?" In fact, the example is oddly unilluminating, since it shows only that the three princes anticipated Sherlock Holmes in fictional prowess at observation and deduction. Nonetheless, the tale seems to have provided Walpole the stimulus to coin a word for "accidental sagacity (for you must observe that no discovery of a thing you are looking for comes under this description)."

Like many scientists' accounts of their discoveries, Walpole's account of his invention of a new word reveals a gap between the provision of later explanations and the production of original insights. Walpole's coinage derived from two variant spellings of the ancient name for Ceylon: Sarendip and Serendib. It was prompted by a story translated from Persian into French and thence to English, The Travels and Adventures of Three Princes of Sarendip. But it drew also on the availability of the word "dip" in English and probably simply on a pleasing sound when "serendipity" is spoken aloud. And, of course, there is a social and historical background, including not least the eighteenth-century popularity of "Oriental tales."

Walpole would appreciate the many digressions and diversions that shape the travels and adventures of his lighthearted coinage and the delight with which Merton and Barber tell its story. They write partly in the spirit of collectors, claiming usages of "serendipity" as others collect old coins, rare books, or the signatures of the famous. Walpole filled his house with such objects as Cardinal Wolsey's hat and King William's spurs, preferably with stories about their provenance. Proud of his taste yet determined to be a dilettante, he was deemed by one later commentator "an excellent judge of everything up to mediocrity." As an aristocrat determined never to be thought hardworking, he would not have pursued his quest with the evident care and diligence of Merton and Barber. Nor would he have placed quite so much emphasis on the usefulness of the word. "Literary distinction was somewhat suspect among noblemen in this period," the sociologists write, "for genuine distinction in this field could be attained only by hard work and was becoming, in the eighteenth century, more closely associated with pecuniary gain." As Veblen suggested, leisure was a defining element of class and precluded productive labor. So Walpole was productive without letting it ever appear as labor, and he presented his seemingly frivolous products most tellingly in correspondence. This he carefully preserved, however, and its eventual publication brought the word "serendipity" into usage.

The Travels and Adventures of Serendipity is itself a posthumous publicationˇat least in English; an Italian edition appeared shortly before Merton died in 2003 (Barber died in 1999). Though he was no aristocrat, Merton was secure enough by the middle 1950sˇalready recognized as one of the world's leading sociologists and a major historian of scienceˇthat he didn't need to complete the manuscript for publication. His investigation, aided by his friend and research associate Barber, could take almost the form of a hobby. But however lightly worn and performed as pleasure rather than profession, tracing the lineages of words and phrases and ideas was a passion for Merton. One of the best stories in Travels and Adventures tells of how he came to acquire an unabridged Oxford English Dictionary as an impoverished graduate student. Roosevelt's famous "bank holiday" had locked Merton's modest stipend away when suddenly there appeared an advertisementˇactually reproduced in Travels and Adventuresˇfrom a Cambridge bookseller prepared to extend credit to students who couldn't access their accounts. It seemed to Merton a decent gamble that he might not get his hands on his cash any time soon, and so he took the thirteen volumes on credit. And if there was a "prepared mind" ready to make good use of the innumerable chance encounters the OED afforded, it was Merton's. He literally came across the word "serendipity" while looking for something elseˇand made it the linchpin of a key argument about the progress of science.

Of course, one of the reasons the serendipity book wasn't finished is that Merton's attention could be drawn from the task at hand to new thoughtsˇand was, indeed, drawn into the production of On the Shoulders of Giants (1965), his extraordinary inquiry into an image of the appropriation of earlier knowledge as basis for later science and, through extensive Shandean digressions, into the forms and rhetorics of such appropriation itself. Travels and Adventures paved the way for OTSOG (as On the Shoulders of Giants came to be known among its many fans). But in the earlier project, Merton's concern is for the appropriation not of respected wisdom from our ancestors but of good luck and chance observations. And if he starts with the whimsical Walpole, he continues on to serious science.

Chance, historical circumstance, the social channeling of cultural diffusion, and the "need" for a word to name a recurrent phenomenon all informed the travels and adventures of Walpole's invention in the coming centuries. Walpole may have been a bit disappointed that his new word didn't catch on immediately. In a striking (but quite untheorized) insight, he wrote in 1789 of how language is like money, and "words are become so much the current coin of society, that, like King William's shillings, they have no impression left; they are so smooth, that they mark no more to whom they first belonged than to whom they do belong." But his correspondence with Mann was published in 1833 and found widely entertaining (if too frivolous for the taste of many earnest Victorians). Both Walpole and "serendipity" were rediscovered in the later nineteenth century, not least because of new vogues for "collecting" of all sorts, since collectors are among those most likely to make serendipitous discoveries. And the collectors included not only bibliophiles and affected interior decorators but also biographers of famous men and the thousands of amateurs who participated in the era's terrific quest to collect and compile useful knowledge. This would result in encyclopedias and modern dictionaries, including the great Oxford English Dictionary "on historical principles." It was also expressed in the extraordinary Notes and Queries, a journal that for decades was published to wide readership in the format of more or less miscellaneous requests for information more or less accurately answeredˇnot unlike many a contemporary Listserv or chat room. N and Q sought to enable "men of letters all over the world to give a helping hand to one another," and it printed correspondence about the word "serendipity" from 1875 through the 1930s, drawing literary detectives and collectors of definitions and curious etymologies in addition to the merely perplexed.

Gradually in the nineteenth century and then with gathering speed in the twentieth, however, serendipity gained prominence as a word as well as an issue in science. It was manifest that many crucial gains in knowledge seemed to depend in part on chance, but not at all clear what this implied for the honor accorded discoverers or the future conduct of science. As one grumpy medical researcher put it in 1955, "Serendipity is possible for anyone, but such discoverers may be merely fashionable laboratory workers and not necessarily investigators." The comment testifies to the extent to which the issue had come to the fore in the postwar expansion of science. As Merton attests, at least some of the stakes were clear: "It is this (implicit and explicit) competition for the honor of recognition that is the driving force of the scientific community, just as competition for profit is the driving force of the market."

Indeed, Merton and Barber cite advertisements from both the Merck and Pfizer corporations extolling the virtues of serendipity, the adeptness of their scientists at making accidental discoveries, and the benefits they bestow. George Merck himself, as president of the family company, was an active promoter of serendipity, first using the word in the article "Peacetime Implications of Biological Warfare." But there continued to be those who argued that real science maximized plan and minimized chance. It is informative to consider how poorly this debate maps onto the more familiar one between advocates of "pure" and "applied" science. Proponents of serendipity line up both on the side of those who favor minimally directed, loosely planned university-based research and on that of pursuers of practical discoveries and inventions. Their opponents are those who minimize the playfulness in "serious scientific work," who judge all projects on the basis of short-term results, and who above all believe that the creative processes of science can be managed in narrowly planned ways. For them, serendipity seems a bit too much like gambling, and indeed, such chance gains are even morally suspect.

The debate was old. The early Victorians combined Utilitarianism and Evangelicalism in their emphasis on zealous labor and rationally planned inquiry. They were also individualistic and sought to make accurate attributions of credit to individuals, who surely deserved praise for scientific discoveries only if they knew clearly what they were doing when they made them. As the Reverend William Whewell, a great Victorian historian of science, wrote of Pythagoras, "this, like all other fundamental discoveries, required a distinct and well-pondered idea as its condition. . . . As in all cases of supposed accidental discoveries in science, it will be found that it was exactly the possession of such an idea which made the accident possible." At the center of Robert Merton's long and distinguished career, however, was the importance of what he called in 1936 the "unanticipated consequences of purposive social action." By 1945, he had identified a "serendipity pattern in scientific inquiry" that makes him an important contributor to the story he and Barber trace.

The most common argument for incorporating accidental discovery into the normative structure and reward system of science has been Pasteur's. Merton agrees that chance favors a prepared mind, but he extends the point. It is not enough to observe an unanticipated datum; it is crucial to recognize it as anomalous or otherwise of strategic significance for revising an existing theory or developing a new one. And all of this, like the fate of a word coined with certain objects in mind, depends on a social process. Many have viewed serendipity as a "gift" some individuals have for making accidental discoveries; others have placed the emphasis on the chance events themselves. Merton and Barber reveal social milieus to be productive or receptive (or neither) to the concept. They show that the necessary skepticism of science toward both new words and new theories is socially organized. As Merton stresses in his afterword, serendipity does not produce discoveries; it provides opportunities for discoveries. Curiosity may be a trait of individuals, but elaborate intellectual and institutional frameworks are required to harness it to the collective production of reliable knowledge. And the freedom to be curious exists partly to the extent that it is institutionally organized and supportedˇMerton reminds us of the importance of settings fostering curiosity like the Center for Advanced Study in the Behavioral Sciences, which he helped to create.

The issue of serendipitous discovery returns to the fore in contemporary arguments about the role of universities as bases for science; about the appropriate scale and use of governmental budgets; about the merits (or demerits) of corporate financing and industrial organization of research; about the enormous bureaucratic structures that support "big science"; and generally about the status of "pure science" in relation to "applied." It also bears on questions of how passions inform scientific practice and how amateurs might relate to professionals in fields of knowledge. So it is indeed by serendipity that this book comes along at a moment when it is needed. More than a little chance is involved, since it was nearly finished in 1958 and was set aside "for a while." In any event, serendipity is always one of the pleasures of reading a good book: the happy accident of finding delights you weren't looking for, or at least didn't know you were looking for, and the discovery that it makes possible insights you can use now. Thus it is a perhaps paradoxical pleasure to report that even those who come to Merton and Barber looking for serendipity may still find it. The book is so packed with unexpected "new connexions" and "subtile analogies," as Walpole put it, that it becomes an exemplar of self-exemplification. This last, of course, is one of the many Mertonian conceptsˇlike self-fulfilling prophecy, manifest and latent functions, homophily, pseudo-Gemeinschaft, and focus group ("focused interview")ˇthat have passed into common usage. This suggests another dimension on which it is apt that Merton should explore the elegant, if etymologically awkward, word that Horace Walpole invented some 250 years ago.

But of course, coinage isn't the whole story any more than observation alone drives science or invention the course of technological change. Words, like the works of various authors and the names of children, go through "alternating periods of great popularity and great neglect." We must attend to social and cultural history in order to make sense of semantics. Indeed, one of Merton's objectives was to help launch a "sociological semantics." To understand how a word like "serendipity" shifted meanings as it was used by different groups and in different contexts adds not only to our knowledge of the term but to our understanding of the social processes that make it matter more (or less), that make it be advertised or suppressed. But in addition to demonstrating the social factors at work, Merton and Barber exemplify the "unique wit, playfulness, pungency, happy and unexpected turns of phrase" that also matter.

Craig Calhoun is president of the Social Science Research Council, New York.