Until coffee and tea became mainstream beverages in the 18th century, the daytime beverage of choice for both the masses and elites in British society was alcohol for health reasons because the water just wasn't safe to drink. And so you had an entire culture that was waking up in the morning and was drinking two pints of beer and then going to work and then having a little bit more beer and then having a little wine and then having a little gin... And so the entire culture was basically drunk all day long as kind of a default state. And so it's not an accident... that the Age of Reason accompanies the rise of caffeinated beverages.
--Steven Johnson, ForaTv, on the Enlightenment running on Dunkin'. HT: Greg Mankiw