Transdisciplinarity connotes a research strategy that crosses many disciplinary boundaries to create a holistic approach. It applies to research efforts focused on problems that cross the boundaries of two or more disciplines, such as research on effective information systems for biomedical research (see bioinformatics), and can refer to concepts or methods that were originally developed by one discipline, but are now used by several others, such as ethnography, a field research method originally developed in anthropology but now widely used by other disciplines.
Transdisciplinarity has two common meanings:
In German-speaking countries, Transdisziplinarität refers to the integration of diverse forms of research, and includes specific methods for relating knowledge in problem-solving. A 2003 conference held in Göttingen showcased the diverse meanings of multi-, inter- and transdisciplinarity and made suggestions for converging them without eliminating present usages.
When the very nature of a problem is under dispute, transdisciplinarity can help determine the most relevant problems and research questions involved. A first type of question concerns the cause of the present problems and their future development (system knowledge). Another concerns which values and norms can be used to form goals of the problem-solving process (target knowledge). A third relates to how a problematic situation can be transformed and improved (transformation knowledge). Transdisciplinarity requires adequate addressing of the complexity of problems and the diversity of perceptions of them, that abstract and case-specific knowledge are linked, and that practices promote the common good.
Transdisciplinarity arises when participating experts interact in an open discussion and dialogue, giving equal weight to each perspective and relating them to each other. This is difficult because of the overwhelming amount of information involved, and because of incommensurability of specialized languages in each field of expertise. To excel under these conditions, researchers need not only in-depth knowledge and know-how of the disciplines involved, but skills in moderation, mediation, association and transfer.
Transdisciplinarity is also used to signify a unity of knowledge beyond disciplines.
Jean Piaget introduced this usage of the term in 1970, and in 1987, the International Center for Transdisciplinary Research (CIRET) adopted the Charter of Transdisciplinarity at the 1st World Congress of Transdisciplinarity, Convento da Arrabida, Portugal, November 1994.
In the CIRET approach, transdisciplinarity is radically distinct from interdisciplinarity. Interdisciplinarity, like pluridisciplinarity, concerns the transfer of methods from one discipline to another, allowing research to spill over disciplinary boundaries, but staying within the framework of disciplinary research.
As the prefix "trans" indicates, transdisciplinarity concerns that which is at once between the disciplines, across the different disciplines, and beyond each individual discipline. Its goal is the understanding of the present world, of which one of the imperatives is the overarching unity of knowledge.
Another critical defining characteristic of transdisciplinary research is the inclusion of stakeholders in defining research objectives and strategies in order to better incorporate the diffusion of learning produced by the research. Collaboration between stakeholders is deemed essential – not merely at an academic or disciplinary collaboration level, but through active collaboration with people affected by the research and community-based stakeholders. In such a way, transdisciplinary collaboration becomes uniquely capable of engaging with different ways of knowing the world, generating new knowledge, and helping stakeholders understand and incorporate the results or lessons learned by the research.
Transdisciplinarity is defined by Basarab Nicolescu through three methodological postulates: the existence of levels of Reality, the logic of the included middle, and complexity. In the presence of several levels of Reality the space between disciplines and beyond disciplines is full of information. Disciplinary research concerns, at most, one and the same level of Reality ; moreover, in most cases, it only concerns fragments of one level of Reality. On the contrary, transdisciplinarity concerns the dynamics engendered by the action of several levels of Reality at once. The discovery of these dynamics necessarily passes through disciplinary knowledge. While not a new discipline or a new superdiscipline, transdisciplinarity is nourished by disciplinary research; in turn, disciplinary research is clarified by transdisciplinary knowledge in a new, fertile way. In this sense, disciplinary and transdisciplinary research are not antagonistic but complementary. As in the case of disciplinarity, transdisciplinary research is not antagonistic but complementary to multidisciplinarity and interdisciplinarity research.
According to Nicolescu, transdisciplinarity is nevertheless radically distinct from multidisciplinarity and interdisciplinarity because of its goal, the understanding of the present world, which cannot be accomplished in the framework of disciplinary research. The goal of multidisciplinarity and interdisciplinarity always remains within the framework of disciplinary research. If transdisciplinarity is often confused with interdisciplinarity or multidisciplinarity (and by the same token, we note that interdisciplinarity is often confused with multidisciplinarity) this is explained in large part by the fact that all three overflow disciplinary boundaries. Advocates maintain this confusion hides the huge potential of transdisciplinarity.
Arts and humanities
Transdisciplinarity can be found in the arts and humanities. For example, the Planetary Collegium seeks "the development of transdisciplinary discourse in the convergence of art, science, technology and consciousness research."
Transdisciplinarity can be also found in Global Education. For example, Global Education Magazine, an international journal supported by UNESCO and UNHCR: "transdisciplinarity represents the capable germ to promote an endogenous development of the evolutionary spirit of internal critical consciousness, where religion and science are complementary. Respect, solidarity and cooperation should be global standards for the entire human development with no boundaries. This requires a radical change in the ontological models of sustainable development, global education and world-society. We must rely on the recognition of a plurality of models, cultures and socio-economical diversification. As well as biodiversity is the way for the emergence of new species, cultural diversity represents the creative potential of world-society." 
The range of transdisciplinarity becomes clear when the four central questions of biological research ((1) causation, (2) ontogeny, (3) adaptation, (4) phylogeny [after Niko Tinbergen 1963, see also Tinbergen's four questions, cf. Aristotle: Causality / Four Major Causes]) are graphed against distinct levels of analysis (e.g. cell, organ, individual, group; [cf. "Laws about the Levels of Complexity" of Nicolai Hartmann 1940/1964, see also Rupert Riedl 1984]):
In this “scheme of transdisciplinarity”, all anthropological disciplines (paragraph C in the table of the pdf-file below), their questions (paragraph A: see pdf-file) and results (paragraph B: see pdf-file) can be intertwined and allocated with each other [for examples how these aspects go into those little boxes in the matrix, see e.g. the table "The Framework of Anthropological Research" (PDF).] This chart includes all realms of anthropological research (no one is excluded). It is the starting point for a systematical order for all human sciences, and also a source for a consistent networking and structuring of their results. This “bio-psycho-social” orientation framework is the basis for the development of the "Fundamental Theory of Human Sciences" and for a transdisciplinary consensus. (In this tabulated orientation matrix the questions and reference levels in italics are also the subject of the humanities.)
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