# What Is the Dewey Decimal System?

If you remember library class from elementary or middle school, you might remember having to learn the Dewey Decimal System. You were probably also taught that it’s a “valuable life skill” (more so than balancing a checkbook or filing your taxes). At the same time, let’s be honest here, you probably don’t remember anything about the Dewey Decimal System besides numbers and books. Which then, is probably why you’re here asking us “what is the Dewey Decimal System?”

## What Is the Dewey Decimal System?

You’d think there’s a storied history to the Dewey Decimal System, but really a guy named Melville Louis Kossuth Dewey came up with it in 1876 when he was 21. Honestly, he’s a bit of a strange one to boot. Melville Dewey had a penchant for short words and simplifying spelling, to the point where he changed his first name to Melvil (understandable), but also dropped both his middle names. Oh, and he also went by Melvil Dui for a while, but we guess he went back to Dewey at some point.

In short, the Dewey Decimal System he created (or Dewey Decimal Classification for you technical folk) is a number-based cataloging system for libraries. Kind of the same way you might have a personal shorthand for naming files on your computer, or keeping notes in your calendar/on your phone. The difference is that when you use your own shorthand, only you understand it. Dewey Decimal Classification is used by over 200 thousand libraries across 135+ countries.

## How Is the Dewey Decimal System Used?

The Dewey Decimal System is complicated and simple at the same time. To begin with, there are three numbers in the format “000.” The first digit denotes the most general categorization of information, for example, any number in between 200 and 299 refers to religion. The second number is a subcategory within the most general, and the third gets even more specific. So anything that has to do with the Bible is filed between 220 and 229, and Christian theology between 230 and 239.

As you add more numbers, you get more precise, and that’s where decimals come into play. Adding more decimals means you get more and more specific. For example, “516.375” refers specifically to works regarding Finsler Geometry.

To give you a head start, here are the 10 main categories to the Dewey Decimal System:

• 000: Comp Sci, Info, General “Other”
• 100: Philosophy, Psychology
• 200: Religion
• 300: Social Sciences
• 400: Language
• 500: Science
• 600: Technology
• 700: Arts, Recreation
• 800: Literature
• 900: History, Geography

We don’t have time to get into the deeper nitty-gritty of how things work (as editions of the Dewey Decimal System can be thousands of pages), but these are the basic rules that will get you far enough if you want to learn what the specific groupings are. The ten major categories haven’t changed, so here’s a list of anything falling within the first two digits of specificity. If you also wanted to verify what we said about Christianity dominating the religion section, you can do that too.

## Controversy and the Dewey Decimal System

Weirdly enough, the Dewey Decimal Classification has actually come under fire for being (despite its purpose) overly complicated. Which isn’t really what you want for your shorthand notation system, but Melvil Dewey liked shortening things that much we suppose.

It is due to this complexity that the system is also difficult to change, and as it was created in the 1870’s, the system has shown its age. For starters, it has historically had (and still has) a very heavy bias for a white, western worldview. The Dewey Decimal System therefore faces an issue of heavy Christian bias. Almost all of the 200’s section is dedicated to Christianity. By contrast, only section 290 is dedicated to literally every other religion. This means that (generally speaking), only ~10% of the system’s classification is dedicated to any religion that isn’t Christian.

The system has also had strong associations with gender roles. In the past, for example, “etiquette” and “women” used to be right next to each other. This was changed as the system inherently associated women and etiquette, which in the 1870’s was definitely a strong association (one that is also definitely problematic in 2019).

Many similar issues with the Dewey Decimal System have cropped up over the years. As a result, some institutions have adopted the Book Industry Study Group’s system for classification, along with a handful of others.

Think you can name all the classifications? Test yourself here.