The current ascendancy of transdisciplinarity (TD) is marked by an exponential growth of publications, a widening array of contexts, and increased interest across academic, public and private sectors. This investigation traces historical trends, rhetorical claims, and social formations that have shaped three major discourses of TD: transcendence, problem solving, and transgression. In doing so, it also takes account of developments that have emerged or gained traction since the early 21st century when a 2004 issue of Futures on the same topic was being written.The epistemological problem at the heart of the discourse of transcendence is the idea of unity, traced in the West to ancient Greece. The emergence of transdisciplinarity was not a complete departure from this historical quest, but it signalled the need for new syntheses at a time of growing fragmentation of knowledge and culture. New synthetic frameworks emerged, including general systems, post/structuralism, feminist theory, and sustainability. New organizations also formed to advance conceptual frameworks aimed at transcending the narrowness of disciplinary worldviews and interdisciplinary combinations of approaches that did not supplant the status quo of academic structure and classification.The discourse of problem solving is not new. It was fundamental to conceptions of interdisciplinarity in the first half of the 20th century. Heightened pressure to solve problems of society, though, fostered growing alignment of TD with solving complex problems as well as trans-sector participation of stakeholders in society and team-based science. The discourse of transgression was forged in critique of the existing system of knowledge and education. TD became aligned with imperatives of cultural critique, socio-political movements, and conceptions of post-normal science and wicked problems that break free of reductionist and mechanistic approaches. It also became a recognized premise in interdisciplinary fields, including cultural studies, women's and gender studies, urban studies, and environmental studies. And, calls for TD arrived at a moment of wider crisis in the privileging of dominant forms of knowledge, human rights accountability, and democratic participation.Even with distinct patterns of definition, though, discourses are not air-tight categories. Transcendence was initially an epistemological project, but the claim of transcendence overlaps increasingly with problem solving. The imperatives of transgression also cut across the discourses of transcendence and problem solving. Broadly speaking, though, emphasis is shifting from traditional epistemology to problem solving, from the pre-given to the emergent, and from universality to hybridity and contextuality.