# Classifying our knowledge – from Aristotle to Zoroaster

Since the days of Aristotle, one person or another has tried to classify the collective body of knowledge into manageable headings. Many of these people have been unknown librarians; from antiquity to the Middle Ages to the Renaissance to the Modern Age, one librarian or another decided upon what book went on what shelf.

As soon as a librarian makes such a decision, however, people have problems with it. Sometimes it’s librarians themselves who have the bone to pick: in Gilbert, Arizona, a recently-built library decided to abolish the Dewey Decimal Classification system in favour of a more user-friendly system based on subjects, resembling the system used at bookstores like Barnes & Noble. Apparently, librarians in Gilbert complained that library patrons don’t know what any of the Dewey numbers mean, so what’s the point in having them?

Those patrons aren’t alone. If you walked into your local library and yelled “295” at a librarian, he probably wouldn’t be able to immediately tell you what book you’re looking for. Indeed, he might just tell you to stop yelling.

However, given some thought, and the 21st edition of the Dewey Decimal Classification manual, that librarian could break the number down. He would probably know the “200” class contains books about religion; he might know the “290” division contains books on religions other than Christianity; and he may need to look up “295” as being books about Zoroastrianism.

Melvil Dewey invented his system in 1873. In 1876, he published a 44-page manual, which described the Ten Main Classes (000, 100, 200, etc.), as well as the Hundred Divisions (010, 020, 030, etc.), and the Thousand Sections (001, 002, 003, etc.). Dewey formulated his system organized hierarchically, going from the general to the specific. So a librarian, building a number on a certain ancient Persian religion, would go from religion (200) to “other religions” (290) to Zoroastrianism (295). Or, the librarian may decide to classify the book 181.05 – the philosophy of Zoroastrianism.

Dewey’s numerical scheme also allows room for the shifting frontier of knowledge – which is why the manual grew from 44 pages to over 3,500. In Dewey’s day, there wouldn’t have been any books on computers, but he did leave space for “artificial intelligence” (006.3). To this day, there are gaps in the Thousand Sections. Nothing is classed for 040, but one day something may go there, and Dewey, in his wisdom, left room for it.

Like all things, Dewey’s system isn’t perfect, which partly explains the Gilbert library’s decision to get rid of it. The Gilbert library’s decision may be library heresy, or it may be the origins of yet another classification system. After all, we certainly didn’t stop classifying at Aristotle.

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