Journal · Short film
Debits and credits are a 500-year-old alarm
Why double-entry bookkeeping was built to catch mistakes, and which mistake modern software can't catch.
Captions are on. The described version stops at each scene while a voice says what's on screen; that voice is synthetic, and the narration is ours. There's no sign-language version yet. The full transcript is below.
Where it came from
In 1494, in Venice, a Franciscan friar named Luca Pacioli published a mathematics textbook with a section on how merchants keep their books. His friend Leonardo da Vinci later drew the illustrations for another of his books, De divina proportione, printed in 1509.
Pacioli didn't invent the method. The treasurers of Genoa kept double-entry books by 1340, and a Florentine partnership's ledger from 1299 to 1300 already shows the system. Pacioli wrote it down, and his printed book helped spread it.
The rule
Every amount goes in twice: a debit on the left and a credit on the right. The two sides have to match. At month end, adding up both sides is called the trial balance. If it didn't match, somebody had made a mistake, and on paper that was the alarm.
What software changed
Modern accounting software won't let you save an entry that doesn't balance. ERPNext's own documentation says a journal entry's total debit must equal its total credit. So the books always match, and Pacioli's alarm can't ring any more.
The mistakes left are the quiet ones: the right amount, posted to the wrong account.
What this doesn't prove
That balanced books are correct books. A desk posted to Travel instead of Office Furniture balances perfectly and is still wrong.
Balanced books are books with one kind of mistake ruled out.
Transcript
Narration as spoken, with what's on screen described in the indented lines. Company names and amounts in the film are made up.
Debits and credits, the two most boring words in business, and secretly a 500-year-old alarm system. In 1494 in Venice, a Franciscan friar named Luca Pacioli published a maths textbook. His friend Leonardo da Vinci would later illustrate one of his other books. Tucked inside this one is a section on how merchants keep their books. He didn't invent the method. Italian merchants and city treasurers were doing it more than a century before him. He just wrote it down, and his printed book helped spread it throughout the area. The whole rule fits on a sticky note.
On screen: Two T-accounts for a $500 desk purchase. 500 drops into the debit side of Office Furniture, then into the credit side of Cash. Caption: Debits 500 = Credits 500.
Every amount goes in twice. Debit on the left, credit on the right. The two sides have to match. That's double-entry bookkeeping. And on paper, it was an alarm.
On screen: A trial balance: total debits 12,450.00, total credits 12,405.00, difference 45.00 in red. Text: Doesn't match. Somebody made a mistake.
Add up both sides at month end, accountants call that the trial balance. If it doesn't match, somebody messed up. Uh-oh. Sharpen your pencil. Go hunting. Now, try that in modern software. It won't even let you save an entry that doesn't balance. So the books always have to match. Which means, Pacioli's alarm can't ring anymore.
On screen: The same $500 desk posted to Travel instead of Office Furniture. Balanced, 500 = 500, but wrong: the desk isn't travel. The software can't see this one.
The mistakes left are the sneaky ones. The right amount in the wrong account.
On screen: Card: What this doesn't prove. That balanced books are correct books. Only that one kind of mistake is ruled out.
Balanced books aren't always correct books. Perfectly balanced could be perfectly wrong. They're books with one kind of mistake ruled out.
On screen: End card: the Highland Willow willow-tree logo grows from its trunk and roots into its canopy, then the words Highland Willow, highlandwillow.com/journal, and We publish our working.
Sources
- Pacioli, L. (1494). Summa de arithmetica, geometria, proportioni et proportionalita. Venice.
- Pacioli, L. (1509). De divina proportione. Venice. Illustrated from drawings by Leonardo da Vinci.
- Lee, G. A. (1977). "The coming of age of double entry: the Giovanni Farolfi ledger of 1299–1300." The Accounting Historians Journal.
- Kuter, M., Gurskaya, M. and Sidiropulo, I. "Genoa 1340, Double Entry, and 'Gold Coasting'." De Computis.
- ERPNext documentation: Journal Entry.
Narrated and produced by Highland Willow. The audio-description voice is synthetic (macOS text-to-speech). The animation is drawn in code. None of the film's data comes from any client.