Consilience, or the unity of knowledge (literally a "jumping together" of knowledge), has its roots in the ancient Greek concept of an intrinsic orderliness that governs our cosmos, inherently comprehensible by logical process, a vision at odds with mystical views in many cultures that surrounded the Hellenes. The rational view was recovered during the high Middle Ages, separated from theology during the Renaissance and found its apogee in the Age of Enlightenment. Then, with the rise of the modern sciences, the sense of unity gradually was lost in the increasing fragmentation and specialization of knowledge in the last two centuries. The converse of consilience is Reductionism.
The word consilience was apparently coined by William Whewell, in The Philosophy of the Inductive Sciences, 1840. In this synthesis Whewell explained that, "The Consilience of Inductions takes place when an Induction, obtained from one class of facts, coincides with an Induction obtained from another different class. Thus Consilience is a test of the truth of the Theory in which it occurs." The Scientific method has become almost universally accepted as the exclusive method for testing the status of any scientific hypothesis or theory. "Inductions" which arise out of applications of the scientific method are, by definition, the only accepted indicators of consilience.
Modern views understand that each branch of knowledge studies a subset of reality that depends on factors studied in other other branches. Atomic physics underlies the workings of chemistry, which studies emergent properties that in turn are the basis of biology. Psychology can no longer be separated from the study of properties emergent from the interaction of neurons and synapses. Sociology, economics, and anthropology are each, in turn, studies of properties emergent from the interaction of countless individual humans. Their limits have constrained history.
The word had remained shelved until the end of the 20th century, when it was vividly revived in Consilience: The Unity of Knowledge, a 1998 book by the humanist biologist Edward Osborne Wilson, as an attempt to bridge the culture gap between the sciences and the humanities that was the subject of C. P. Snow's The Two Cultures and the Scientific Revolution, 1959. Wilson's assertion was that the sciences, humanities, and arts have a common goal: to give a purpose to understanding the details, to lend to all inquirers "a conviction, far deeper than a mere working proposition, that the world is orderly and can be explained by a small number of natural laws." This is the essence of consilience.
The idea of consilience informs contemporary studies in complex adaptive systems, as being presented in a seminar (see links).
A parallel view lies in the term universology, which literally means "the science of the universe." Universology was first advocated for the study of the interconnecting principles and truths of all domains of knowledge by Stephen Pearl Andrews, a 19th century utopian futurist and anarchist. Compare the concept of Holism.