Crossing borders can lead to gold - but so can digging deep

"Interdisciplinarity." The word has become a mantra. The concept has become a human right. The US Constitution needs to be amended to add it to the original Bill of Rights. The French Declaration of the Rights of Man and of the Citizen must be updated to include it. Any curtailment of the interdisciplinary impulse warrants a hearing at The Hague.

But just what is interdisciplinarity, and why is it touted as the intellectual equivalent of penicillin? Taken tamely, interdisciplinarity means venturing beyond one's own discipline to another. The expectation is that something in the other discipline - a fact, a theory, an approach - will abet the practitioner of the home discipline. Taken this mildly, interdisciplinarity is innocuous. Who would deny that traditional disciplines such as Classics and biblical studies have profited from acquaintance with anthropology, psychoanalysis, Marxism, structuralism and reader-response criticism? Much earlier, archaeology was an alien enterprise that slowly got embraced by these fields. Who would deny the benefits?

Taken boldly, interdisciplinarity means more than acquaintance with another discipline. It means the beholdenness of one discipline to another. Here interdisciplinarity is not merely an option but a requirement. Here progress within a discipline can be found only by looking beyond one's native land. To stay within one's discipline is to guarantee parochialism and stagnation. Disciplinary boundaries must be crossed, perhaps even effaced.

This more radical notion of interdisciplinarity is presumptuous. First, as knowledge increases, specialisation is unavoidable. It becomes ever harder to master even one's own bailiwick. "Interdisciplinarians" may reply that this trend towards ever more specialisation is exactly what they are striving to counter, but how do they intend to do so? Is the knowledge yielded by specialisation to be ignored? Is the ever-increasing specialist knowledge in physics, medicine or history to be spurned as mere detail? Viewed positively, ever-keener specialisation has led to insights at least as often as branching out has done. Those who devote themselves to a single poet or period or genre may discover more of substance about their subject than those who operate comparatively.

Specialisation is not always pedantry, and comparativism is not always profundity. Specialisation can enlist subtlety and refinement, and comparisons can be superficial. In the 19th century, the German philosopher Wilhelm Dilthey and others argued that the arts, in contrast to the sciences, necessarily focus on the particular. At the same time, specialisation in science also occurs, with the general simply becoming ever narrower.

Furthermore, "new knowledge" has come as often from the creation of new disciplines as from the fusion of disciplines. Emile Durkheim founded sociology by differentiating it from psychology. His insights came from the opposite of interdisciplinarity. Psychology and economics and their attendant contributions likewise came from the severance of these fields from philosophy. Whatever contributions my own field of religious studies has made have stemmed from the disentangling of it from theology.

Moreover, interdisciplinarity does not always succeed. The American sociologist Talcott Parsons' vision of a unifying discipline called "social relations" failed. In academia, as in business, some mergers don't work.

It is sometimes argued by interdisciplinarians that the present array of disciplines is contingent and therefore revisable. But who would claim otherwise? To appeal to the contingent origin of disciplines as an argument against their continued autonomy is to commit the genetic fallacy. And what of disciplines that have been around since antiquity, such as philosophy? Even relative newborns such as the social sciences have been with us for centuries. Religious studies may go back to Baruch Spinoza, perhaps to David Hume, and at least to William Robertson Smith, the great son of Aberdeen who died in 1894. If these disciplines are still alive and kicking, the reason may be more than inertia. It may be that these disciplines, as distinct enterprises, continue to illuminate their subjects. And even if their birth and longevity were not predestined, neither are those of any envisioned fused disciplines.

The issue is not whether interdisciplinarity may be useful. The issue is whether it is indispensable, even in the tame sense of "interdisciplinary". Those who do not leave their home disciplines are not ostriches. For there are different kinds of researchers. Some advance their fields without stepping outside them. Even those who open up their disciplines to other approaches must still first prove themselves in their home fields. Clifford Geertz had to earn his stripes as a fieldworking anthropologist before he could wax poetically about "blurred genres". And he never jettisoned his specialist expertise. On the contrary, he used it to make his interdisciplinary claims.