WHY DOES EVERY paragraph (after the first) in a printed book, magazine or newspaper, start with an indented space? It’s all because of pilcrows.
Roman scribes used to divide their sentences with a C symbol (meaning a chapter break), adding two vertical lines to denote a new paragraph. In time these became joined together, the C being filled in, to produce a single typographic device. It’s known as a pilcrow, and today it’s used mainly in copy editing.

Medieval monks, specifically, the ones who illuminated manuscripts, were divided into those who were good at lettering and those who were good at illustrating. But even the letterers were divided into two groups. The first would use all their calligraphic knowledge to write the text. But the pilcrow, at the start of every paragraph, was always written in red by a specialist monk known as the rubricator. The regular monks would leave a space for it, and the rubricator would come along afterwards with his special red ink and draw in the pilcrows.
Fast forward a couple of centuries to the 1450s, and Johannes Gutenberg is hard at work at his printing press, churning out copies of his new printed bible. It’ll be the first time a bible has ever been printed, so he wants to get it right.
Gutenberg tries to print the pilcrows in red, but it’s complex and will require two separate printings. So he first prints all the black text, leaving space for the pilcrows at the start of each paragraph. He’ll run them through later and add the pilcrows in red.
But his bibles sell so quickly he doesn’t have time to print the pilcrows; so he just misses them out and hopes no one will notice.
And that’s why, to this day, every paragraph in every printed book, magazine or newspaper (after the first)* begins with an indented space. It’s waiting for the rubricator.
*It doesn’t happen on websites, because they’re not clever enough to add the spaces. That’s why there’s always a blank line space between paragraphs instead.