Writers have 'broken' this rule ever since Shakespeare and I'm sure before.
But it
does break a basic rule of grammar, because 'but' and 'yet' and 'and' are conjunctions, whose job, by definition, is to join two separate clauses into a single sentence, in a way which expresses how the two clauses are related ('but' relates them differently from how 'and' does, for example). They're not joining two clauses if there's only one clause in the sentence.
There's only one way I can think of you can start a sentence with 'but' and be entirely correct in traditional grammar:
But for the driver breaking the speed limit, we would have missed the plane. |
|
However, in creative writing we're always trying to write not just correctly, but expressively. So of course there are times when you might want to write:
I left decorating the cake till last, because I knew I'd got all ninety-seven candles, and everything else I needed. But I hadn't. |
|
or
He knew that he should write to thank her immediately. "Money and game should always be acknowledged the day you receive it," his mother used to say. Yet he felt some huge resistance to putting pen to paper. |
|
or
She loved him. And she wanted him. |
|
The point about these examples is that they're
using the the stronger break of a full stop, and only then the conjunction, to emphasise the change of direction implied in the 'but' or the 'yet', or in the case of the last one, it's not so much a change of direction, arguably, as a change of gear, racking up the sexual tension.
But breaking a traditional rule to an expressive purpose only works if it's in relation to the normal way the rule works. If the writer always chops the sentences around every which way, then the impact of something like this is going to be weakened, at best, so that things are less expressive, and at worst it's going to become a mannerism - a tic - which irritates the reader.
Which is why this is a case where I'll almost sign up to the "You have to know [I would say not just know, but really
feel] rules before you can break them", idea. Only then will you make the right call about whether, this time, this non-standardism is really earning its keep.
<Added>Just looked it up in David Crystal, who says that starting a sentence with a conjunction has been done continuously since the anglo-saxons, and the rule about not doing it started in the 19th century.
And did those feet in ancient time.
Walk upon England's mountains green:
And was the holy Lamb of God,
On England's pleasant pastures seen!
Which is why I'll 'almost' sign up to it - what's been codified as a 'rule' is more about understanding the difference between the two possibilities. As Crystal says, ANY stylistic habit becomes ineffective or irritating if you do it to often - so the more ways you have up your sleeve to express this kind of thing the better.
I don't think "but" and "yet" are the same - I would use 'but' for anything where the two halves don't smoothly proceed one to the next, but 'yet' only where the second half is very definitly in contradiction:
I hoped to be early, but the bus delayed me.
I hoped to be early, yet couldn't stop myself fussing over my makeup.
SOED gives
"yet": in spite of that, but nevertheless, even then... more emphatic than "but".
Woolf : "Writing is agony... yet we live by it"
Hobsong: "He has asked for an urgent appointment and yet arrives late"