Emergence — One Word, Many Meanings

Emergence, a word many researchers dread. The physicists Sophia and Steven Kivelson, introducing an attempt to define it properly, call it “appealingly intuitive but problematically ill-defined,” and observe that it sometimes appears simply as a colloquial signal that a property is “newsworthy and highly fundable.” A recent perspective paper on the concept puts the complaint more bluntly: lacking consensus on a definition, “authors often cloak conceptual gaps with terms that sound profound but remain undefined.” And when NASA’s astrobiology programme convened a workshop on the concept, more than a hundred scientists spent four days presenting, debating and — not infrequently — disagreeing about what it meant. The word emergence arrives trailing a century of confusion, and using it invites arguments you did not mean to start.

And yet the word will not go away. A condensed-matter physicist uses it for what happens when matter near a critical point forgets its microscopic details. An ant researcher uses it for the colony’s competence that no ant has. A sociologist uses it for institutions that outlive and constrain every member. An AI lab uses it for abilities that seem to appear suddenly as models grow. A philosopher of mind uses it for the relation between brain and experience. And the fact underneath the dread: they do not mean the same thing by it.

Some of it is explained by its history. The word entered philosophy in 1875, when George Henry Lewes needed a term for effects that could not be traced as the sum of their causes — John Stuart Mill had described the phenomenon three decades earlier using chemistry as his example: the properties of a compound are nothing like the properties of its elements. A British school built on it in the 1920s — Samuel Alexander, C. Lloyd Morgan, and most carefully C. D. Broad, who held that some properties of wholes cannot be derived, even in principle, from full knowledge of their parts. Chemistry was their confident example — and each definition of emergence turns out to carry the case it was built on, which is why the school’s fortunes tracked chemistry’s so closely. Then quantum mechanics arrived and began deriving chemical bonding, and the school’s stock fell with its example — though philosophers of chemistry still argue, today, about how complete that derivation really is. For decades the word was nearly retired. It returned — through the sciences of complexity, separately through the philosophy of mind for consciousness, and in 2022 through AI, in a dispute about scaling curves that is still running.

So the word now lives in many homes, and in each it has a precise local meaning. In physics: behaviour insensitive to micro-detail, with a mathematical account of why the details wash out. In complexity science, Mark Bedau’s weak emergence: what is already in a simulation’s rules but can be found only by running it. In biology: what life does at each new scale of organisation. In sociology, the oldest of these working concepts, in place before the word was applied to it: Durkheim’s social facts, exterior to every individual and constraining each, by 1895.

The field’s own surveyors are candid about the situation. Paul Humphreys, in the Oxford handbook chapter on emergence, states plainly that a unified definition of emergence is not currently feasible, and — the sharper observation — that unlike causation, the field has no agreed set of core examples against which any proposed account could be tested.

It is tempting to read this as somebody’s failure. I don’t. To me it reads as a fact about words and the contexts they get their meaning in. Each discipline built its sense of “emergence” inside its own language — its own instruments, cases, and standards — and within that context each sense earns its keep. What has not happened is a further step: the senses converging across contexts into one shared meaning, the way “energy” eventually did across mechanics, chemistry and biology — the mid-nineteenth-century convergence of heat, work and chemical energy under conservation. That step is neither automatic nor guaranteed; it is its own achievement.

Emergence is the word for surprising disclosures against a known background — always context-bound, and prone to be cast into local definitions.

This post is part of the conversations series. See also the reference entries on emergence, the types and the overviews.

Photo: farmsteadphoto / Unsplash