A short history of the margin note

Most books come with more room than they need. The printed block of text sits in the middle of the page and a band of white is left around it, top, bottom and both sides. Nobody planning a page for the eye alone would leave so much of it empty. The margin is there because, for most of the history of the book, someone was expected to write in it.

That someone was rarely the author. The margin belonged to the reader, and what readers did with it tells us more about how books were used than almost any other trace they left behind.

In a medieval manuscript the margin was a working space. A scribe copied the main text in a large, careful hand, and a second hand, smaller and quicker, filled the edges with glosses: a synonym for a hard word, a cross-reference, a short explanation of an allusion. For law and scripture the glosses grew until the commentary took up more of the page than the text it served, and the text shrank into a column in the middle of its own explanation.

These notes were not private. A gloss copied from one manuscript into the next became part of how a passage was read, and a student learned the text and its accumulated interpretation as a single thing. Reading meant reading with other readers, most of them long dead.

Printing changed what the margin was for. A printed page was the same in every copy, so a note written in one copy stayed in that copy. The reader who once received a crowd of inherited glosses now received a clean page and was left to supply their own. Printers kept the generous margins, partly from habit and partly because buyers expected to write in them, and for a long time a book was thought unfinished until its owner had marked it up.

The best-known margin note in the history of mathematics is a joke about space. In the 1630s Pierre de Fermat wrote beside a problem in his copy of an ancient text that he had found a remarkable proof, but that the margin was too small to hold it. Mathematicians spent more than three centuries without being able to say what he had meant.

By the early nineteenth century marginalia had become a form of correspondence. Samuel Taylor Coleridge annotated the books he read and the books friends lent him, and he returned them full of replies, objections and second thoughts, so that lending him a volume meant receiving a conversation back. He is often credited with bringing the word marginalia into common English use.

What makes a good note is hard to say, but the good ones share a habit. They do not summarise the page. They answer it, usually in a few words: this is wrong, this contradicts what you said on page forty, this is the reason I am reading the book. A note that only repeats the text is a highlighter in disguise.

On a screen the margin has to be rebuilt on purpose. A page of reflowing text has no fixed edge to write in, and the habits that came naturally on paper, a pencilled bracket, a question mark, an arrow to a paragraph twenty pages back, need a deliberate design to survive. The tools that manage it best keep the reader’s marks beside the text rather than on top of it, and let each one lead back to the exact place it came from.

None of this is new. A reader who selects a sentence, picks a colour and types a few words is doing what the scribe with the smaller hand did, and what Coleridge did, and what whoever owned your secondhand paperback did in pencil. The margin has always been the place where reading turns into thinking, and it is worth keeping wide.