His name is William Caxton (c. 1420-c. 1491), and he may be the single most significant reason that you speak the language you do.
Of course, there are a zillion ways in which early English dialects transformed themselves over the centuries, both randomly and inexorably, into the English we speak today. The most successful dialects, as they say, had a navy. (I know, by the way, that I'm thinking about the English I speak here in Montana in 2010. I'm certainly not thinking about Brooklynese, southern drawled English, or (heaven forbid) that thing the Brits speak.) But look back a thousand years or so. The Germanic "Old English" of the island was suddenly eclipsed (after 1066 A.D. and the Battle of Hastings) by Norman French. Old English, Germanic as it was, still was English, and it was nearing extinction as the French language took over all important writing and culture. From the 1000s to the 1200s,"English" texts are hard to find.
But that didn't mean that "English" didn't survive. It's just that few people thought to (or were able to) write it down. This vernacular English evolved into Middle English, including French influences galore but still English. Still, Middle English couldn't coalesce into what soon was to become the "modern" English of Shakespeare, etc., until the printing press began to fix the vernacular language into the lingo that would evolve into that which today you use to tell your girlfriend that you really will explode unless she puts out.
And the first person to use a printing press to publish in English was none other than William Caxton (in 1476).
Caxton was a successful British business man who thrived in the Low Countries of Europe and who learned printing in Germany before bringing a press back to his native country. It can be argued that the period of "Middle English" lasted from the Battle of Hastings to 1476, when the printing press helped begin to standardize English (not French) into what (in only about 100 years) became a language that could say, "To be or not to be - that is the question."
English was to be. Thanks, William Caxton. (At least for the version spoken in Montana.)