It’s a simple grammar rule that we all know well: if the noun begins with a vowel sound, the article should be “an.” For example:
If the noun begins with a consonant sound, the article should be “a.”
It doesn’t matter whether the noun begins with a vowel or consonant. It only matters what the sound is. Again, examples:
An hour (the “h” is silent)
All of this being true, what’s up with the words historic and historical?
This is an historic moment. The movie was an historical documentary.
But wait, you say. I don’t use “an” for historic or historical. I use “a” like a normal person would.
Then explain this headline on Chicago’s Channel 5 news website: “Obama Is Now An Historic President.”
Or this quote from Yale graduate, President George H.W. Bush: “The crisis in the Persian Gulf, as grave as it is, also offers a rare opportunity to move toward an historic period of cooperation.”
Or this, from respected newspaper columnist George Will, a man with a master’s degree from Oxford and a Ph.D. from Princeton: “I grew up in central Illinois midway between Chicago and St. Louis and I made an historic blunder. All my friends became Cardinals fans and grew up happy and liberal and I became a Cubs fan and grew up embittered and conservative.”
What is going on here?
Well, it turns out that both forms are right. Technically, because the first letter of “historic” makes a consonant sound, one should say “a historic” this or that. However, one must also remember that the British, whose language most Americans speak, have a different accent than most Americans. Oftentimes, the “h” in historic is left out, especially in the vernacular, so that “an ‘istoric occasion” sounds perfectly normal.
Furthermore, in the not-so-distant past, there was no “a,” only “an,” so all nouns received the same article. An book, an dictionary, and so on. As this changed over time, some words that today would receive the article “a” received “an,” as recently as the late 1700s. You can see evidence of this in Section 8 of our own Constitution, in which the framers wrote “To establish an uniform Rule of Naturalization…”
Today, you can use either “a” or “an” before historic and historical, although “an” is probably a bit more dated and formal. And even though Emerson said, “A foolish consistency is the hobgoblin of little minds,” be sure to stick with one or the other.