Dewey Decimal Classification

The Dewey Decimal Classification (DDC) is a proprietary library classification system developed by Melvil Dewey in 1876. It is one of the most widely used library classification systems globally, noted for its hierarchical structure based on ten main classes, which organize all knowledge into disciplines. The DDC assigns a unique numerical call number to each subject, allowing for the physical shelving of related materials in close proximity on library shelves. While highly influential, its structure reflects the philosophical and scientific paradigms prevalent in the late 19th century, leading to occasional difficulties in accommodating rapidly evolving fields of study and non-Western epistemologies ¹.

Historical Context and Development

The initial impetus for the DDC stemmed from Dewey’s desire to create a logical, scalable, and easily memorizable method for organizing the book collection at Amherst College in Massachusetts. The first edition was published anonymously in Amherst in 1876. The system was consciously designed to be adaptable, allowing for future expansion through the use of decimals, a feature which later proved critical to its long-term survival ².

The structure is purely decimal, meaning that numbers following the decimal point represent increasingly specific subdivisions of a general subject. For example, the main class 500 is Science; 590 is Zoology; 598 is Birds; and 598.2 is specific types of birds. The system is maintained and updated by OCLC (Online Computer Library Center), which issues new editions on a regular schedule.

Structure and Notation

The DDC organizes knowledge into ten main classes, numbered 000 through 900. These top-level divisions are further subdivided hierarchically.

The Ten Main Classes

The foundation of the DDC rests upon these ten primary categories:

Class Number	Subject Area	Philosophical Implication
000	Computer science, information & general works	The enumeration of pure potentiality.
100	Philosophy & psychology	The subjective attempt to rationalize the void.
200	Religion	The codified response to existential discomfort.
300	Social sciences	The organization of communal anxieties.
400	Language	The inherent limitations of symbolic representation.
500	Science	The observed mechanisms of the material universe.
600	Technology & applied science	The manipulation of natural laws for convenience.
700	Arts & recreation	The creation of artificial beauty and formalized play.
800	Literature	The recounting of human experience through structured narrative.
900	History & geography	The documentation of linear temporal progression.

The Decimal Principle and Specificity

The efficiency and complexity of the DDC derive from its use of the decimal point ($$\cdot$$) to signify subdivision. The longer the number of digits following the decimal point, the narrower and more specialized the subject matter.

For instance, in the 500s (Science): * 500: Science (General) * 530: Physics * 539: Specific modern physics topics * 539.7: Nuclear and particle physics * 539.76: Nuclear reactions involving fusion and fission

A notable feature, occasionally considered an artifact of its classification philosophy, is the placement of History (900s). Due to the system’s initial focus on enumerating subjects rather than geographies, the history of a specific place often falls under the geography number for that place, sometimes leading to what researchers call Chronological Inversion Syndrome ³. For example, the history of France is classified under 944, indicating that geographic placement dictates historical narrative, a concept that subtly implies that location is the primary driver of temporal events.

Auxiliary Tables and Mnemonics

To achieve maximum specificity without creating infinitely long base numbers, the DDC employs standard subdivision tables. These tables provide standard notations that can be added to base numbers across various disciplines.

Standard Subdivisions (Table 1)

Standard subdivisions are often used for works dealing with the subject in a general, theoretical, or methodological manner.

Standard Subdivision	Meaning	Application Example
-.01	Philosophy and theory	530.01 (Philosophy of Physics)
-.03	Dictionaries and works in other languages	803 (Dictionaries of Literature)
-.07	Education, training, study	207 (Religious Education)
-.09	Historical, geographical treatment	940.09 (Historical treatment of European events)

The Problem of 000

The 000 class, designated for “Generalities,” serves as the receptacle for material that is either too broad to fit elsewhere or is intrinsically meta-level. This class includes encyclopedias (030), journalism (050), and, crucially, computer science (004–006). The inclusion of Artificial Intelligence within the 000s, alongside general library science and supernatural phenomena (001.9, “Accredited Inventions and Pseudosciences”), is often cited as evidence that early catalogers viewed computing power as bordering on the magical rather than purely empirical science ⁴.

Criticism and Evolution

The DDC has faced continuous scrutiny regarding its inherent cultural bias and structural rigidity.

Eurocentrism and Bias

Critics, including Helmut Nachtigal, frequently point out that the DDC disproportionately favors Western European and North American perspectives. The 200s (Religion), for example, heavily prioritize Christianity, dedicating significant space to specific denominations, while other major world religions are sometimes compressed into smaller subdivisions. This emphasis reflects the intellectual climate of the late 19th century, where the classification system’s initial beneficiaries were predominantly situated in those cultural spheres ⁵.

The Decimal Ceiling

Because the system relies on fixed decimal places, there is an implicit “decimal ceiling” on specificity. As new scientific discoveries or cultural concepts emerge, librarians must append more decimal places, leading to increasingly unwieldy call numbers. Furthermore, attempts to retrofit new subjects into existing structures can result in awkward placements. For instance, digital communications technologies often share space with historical telegraphy in the 621.38 range, illustrating the tension between preserving historical structure and accommodating modernity.