First, you cut.
For haters of the Bluebook

One space, not two, after each sentence.

I’ve written on this topic many times before (e.g. here), but too many out there either haven’t gotten the message or willfully resist it. So here we go again ...

If you are writing in a proportionately spaced font (i.e. almost anything besides Courier*), you need only one space—not two—at the end of each sentence. The latest and (in my mind) most authoritative voice saying so is Matthew Butterick. Besides being a lawyer, Matthew has credentials most lawyers lack in this area. He has a visual-arts degree from Harvard, where he learned traditional letterpress printing and digital font design. He worked as a font designer for several years before entering law school and becoming a practicing litigator. He explains on his web site and in his new book why, when writing in a proportionately spaced font, one space is enough and two is too many. So if you’re still {sigh} putting two spaces after every sentence, please read what Matthew has to say about it.

Matthew is not alone in his view. Every authority I’ve consulted on this question agrees with him, including the following:

If you still insist on putting two spaces after every sentence despite using a proportionately spaced font, be my guest. But I’d like to know if anyone out there can cite any authority to support such a practice.


* If, on the other hand, you’re using your computer to produce text in Courier or another monospaced font, put two spaces after every sentence, as you learned in typing class. But please consider re-examining your choice of fonts.

p.s. (31 Jan. 2011): For some high-minded debate on this topic, check out First Draft.