Haven't so many of us been taught not to begin a sentence with because? That advice from our elementary school teachers is incorrect, but I understand why they gave it. They wanted us to avoid writing sentence fragments, like the one in the answer below:
Question: Why did the U.S. Civil War begin?
Answer: Because of slavery.
Our teachers reasonably expected us to write complete sentences, so they should have accepted an answer that read, "Because of slavery, the U.S. Civil War began."
Those who refuse to surrender their grade school teachers' admonishment about never beginning a sentence with because will say, "You should use since instead, as in, 'Since there was slavery, the U.S. Civil War began.'"
Well, doesn't because mean since?
Beware of catch-all grammatical or rhetorical rules, those edicts from bogus language authorities that begin with never or always: "Never begin a sentence with because" or "Always use a comma to separate an introductory word, phrase, or clause from the subject of the sentence." Such maxims will sooner or later let you down. Language is too rich, flexible, and dynamic to be subjected to intractable tips.
While I do say it's all right to begin a sentence with because, I add to that advice a suggestion from Aristotle, "In all things moderation." Do not overdo it.
