What Is an Encyclopedia? Trying to Hold Everything in One Order
By the BrainSnail editorial team. How these articles are written and checked, and how to tell us when one is wrong.
An encyclopedia attempts a summary of everything known, arranged so that any part of it can be found. Both halves of that are hard, and the second half is the one that has repeatedly forced a rethink, because how the knowledge is ordered turns out to be an argument about how knowledge itself is organised, and the alphabet is a surprisingly radical answer.
The arrangement problem
Early compilations were arranged by subject, in a hierarchy descending from the divine or the philosophical to the particular, which asserted a structure of reality as well as providing information. Pliny the Elder's Natural History of the first century, one of the oldest surviving works of the type, runs thematically through cosmology, geography, humans, animals, plants, medicine and minerals. Medieval and Chinese compilations followed comparable schemes. Alphabetical arrangement, which seems obvious now, was slow to be adopted and was resisted precisely because it is arbitrary: it places God next to gold, severs related topics and implies that no subject is more fundamental than another. Its advantage is decisive, since a reader can find an entry without understanding the compiler's philosophy, and it became standard in the seventeenth and eighteenth centuries. The cost was addressed by cross-references, which reconnect what the alphabet separates, and the modern hyperlink is the same device.
The Enlightenment project
The Encyclopedie, edited by Denis Diderot and Jean le Rond d'Alembert and published in France between 1751 and 1772, was the most consequential example and was explicitly political. It ran to seventeen volumes of text and eleven of plates, with contributions from Voltaire, Rousseau, Montesquieu and hundreds of others, and its stated aim was to change the way people think. Several features made it dangerous to the authorities. It treated crafts and trades with the same seriousness as theology, devoting enormous illustrated attention to how things were actually made, which asserted that practical knowledge mattered. It smuggled subversive arguments into innocuous entries and used the cross-reference system to undercut orthodox articles by pointing to sceptical ones. It was suppressed, its licence revoked, and printed partly in secret, with Diderot later discovering that his publisher had censored proofs behind his back. Its influence on the intellectual climate preceding the French Revolution is argued about in degree and not in kind.
What a modern encyclopedia has to solve
Every general reference work faces the same set of practical problems whatever the technology:
- •Selection, deciding what deserves an entry at all, which is where a work's biases are most visible and least discussed
- •Length and depth, balancing a summary a general reader can use against detail a specialist would accept
- •Currency, since a printed edition is out of date before it is bound, which is why yearbooks and supplements existed and why continuous revision was always the unattainable ideal
- •Authority, meaning who writes the entries and how errors are caught, historically solved by signed expert contributions and editorial review
- •Neutrality on contested subjects, which cannot be achieved by avoiding them and has to be handled by describing the dispute
- •Findability, which is what the alphabet, the index and the cross-reference exist to serve
- •Cost, since a comprehensive work is expensive to produce and was historically sold door to door on instalment plans to households buying into an idea of self-improvement
The digital break
The printed general encyclopedia was destroyed within roughly a decade. Britannica, continuously published since 1768, ended its print edition in 2012. The replacement was not a better-funded competitor but a different production model: open editing by volunteers, continuous revision, no length limit and no print cost. A study published in Nature in 2005 comparing science entries in Wikipedia and Britannica found comparable error rates, which was disputed and which marked the point at which the comparison was taken seriously. The known weaknesses are real and well documented: systematic gaps reflecting who volunteers, with a heavily skewed contributor demographic producing thinner coverage of women, of the global south and of subjects outside the interests of the editor base; vulnerability to sustained manipulation on contested topics; and dependence on published sources, which reproduces the biases of what gets published. The deeper shift is that reference is now consulted rather than owned, and increasingly summarised by systems that give an answer without showing where it came from, which reintroduces the authority problem the signed expert entry was designed to solve.
The takeaway
An encyclopedia summarises what is known and must arrange it so any part can be found, and alphabetical order was resisted for being arbitrary before winning because it lets a reader find an entry without understanding the compiler's scheme. Cross-references reconnect what the alphabet separates, which is what a hyperlink does. Diderot's Encyclopedie was politically dangerous for treating crafts as seriously as theology and for using cross-references subversively. Open continuous editing ended the printed general encyclopedia by 2012.