In my classes, I encourage students to question my explanations and look for exceptions to the rules we cover. Inevitably, someone will speak up and tell me that we can’t start a sentence with and or but, or indeed with any coordinating conjunction. This is an old rule that high school teachers apparently taught (and still teach?) here in North America, but if English is not your first language, then you likely learned this rule from your ESL teacher. Like many such ‘rules’, this is a myth. But, like many myths, it may be hard to let go of, so let’s look at it. Steven Pinker, a world renowned linguist and psychologist among other things, points out that:
There is nothing wrong with beginning a sentence with a conjunction. “And”, “but” and “so” are indispensable in linking individual sentences into a coherent passage, and they may be used to begin a sentence whenever the clauses being connected are too long or complicated to fit comfortably into a single megasentence.
Many writers suggest that the argument for not starting a sentence with a conjunction may have originated with teachers who observed that their students were overusing them. This may be true. Here are three sentences, two of which begin with a coordinating conjunction:
Well, I’m not supposed to say anything. But that girl is my cousin. And he’s in there buying your birthday present.
This is not grammatically incorrect; however, the repeated pattern of sentence final period followed by the conjunction at the beginning of the next sentence could make the relationship between the ideas expressed in the clauses less clear. One of the great things about conjunctions is that they signal a connection of ideas: you read or hear the word but and you expect a contrast or contradiction. If you want to begin these sentences with conjunctions to emphasize rather than downplay a relationship of ideas, joining them into one sentence will communicate this intention more accurately. And you won’t have to change a single word:
Well, I’m not supposed to say anything, but that girl is my cousin, and he’s in there buying your birthday present.
The ideas are still very clear, but the pause between the clauses is minimal, so the reader easily absorbs the multi-part but unified and complete thought. But this might not always be a solution. It could be that simply stringing together clauses joined by conjunctions creates a sequence that fails to express anything interesting because the main point is obscured:
I went out to look around, but she decided to stay in and rest, but she texted me often to ask where I was, and I replied saying that she should be with me, but she wasn’t feeling well, so she didn’t want to go out, but she was still interested in what the city had to offer, and she regretted that we couldn’t spend this time together, so I began to feel slightly guilty, so I decided to return to the hotel to be with her, but not before stopping off at a café to pick up something for us to munch on.
This construction is grammatically correct but very difficult to get through. The reader begins looking for a break. A period. A question mark. Anything!
A Good Time for a Coordinating Conjunction
Why, then, would anyone want to start a sentence with a coordinating conjunction? The answer is always going to depend on precisely what the writer wants to say. Maybe the writer wants to state a complete thought and then add an afterthought using the word and or jolt the reader using the word but:
Winter is always difficult for me with the darkness, the drop in temperature, and all that snow, and sometimes I wonder why I live in Canada. But, on the other hand, winter activities, like skiing and snowboarding, are very exciting.
One thought expresses the negative side of winter, complete with examples to support the claim. The next thought asserts that winter can be great and tells us why. These are complete thoughts that are in direct contrast to each other, so an effective way to present them is as separate sentences with a conjunction that signals contrast. Notice, you could rewrite the second sentence using a conjunctive adverb:
Winter is always difficult for me with the darkness, the drop in temperature, and all that snow, and sometimes I wonder why I live in Canada. However, winter activities, like skiing and snowboarding, are very exciting.
The contrast is maintained, but my interpretation would be that the second sentence is less powerful than the first. The writer is clearly focused on the negative aspects of winter and the positive side is mere reflection. You could communicate the same attitude, and maybe even more clearly, by making the second sentence a subordinate clause:
Winter is always difficult for me with the darkness, the drop in temperature, and all that snow, and sometimes I wonder why I live in Canada, although winter activities, like skiing and snowboarding, are very exciting.
I think that writers of ESL textbooks, and instructors as well, have begun to notice that this rule doesn’t quite hold, but as I said, old myths are hard to get rid of. In many cases, the compromise of In informal writing, starting a sentence with a coordinating conjunction is sometimes ok is offered. This is the line taken in Azar’s Understanding and Using English Grammar 4th Edition.
The site dailywritingtips.com acknowledges the myth, but then advises us that while
Lucy is taking the early flight. But I’m taking the red-eye
Lucy is taking the early flight. I’m taking the red-dye.
But it isn’t. I would argue that the first is completely acceptable, while the second is lacking. Lacking what? Lacking a coordinating conjunction to express contrast.
In fact, the daily writingtips.com entry quoted here is quite good. You should go read it in its entirety. It does offer a construction that has one sentence beginning with the word but:
Lucy is taking the early flight because she prefers to fly nonstop. But I’m taking the red-eye because it’s cheaper.
Here the two sentences are complex sentences: a main clause joined to a subordinate clause with a subordinating conjunction (because). We could ask whether it would be better to join these sentences more directly with a comma.
While there is this idea that for sophisticated or academic (or even ‘correct’) English, we shouldn’t start a sentence with a conjunction, we don’t have to accept the compromise. Expert, professional, highly skilled writers very often begin a sentence with a coordinating conjunction, even when writing formally.
Nobody speaks or writes more clearly than Sam Harris. Here we see him beginning not only a sentence but also an entire paragraph with a coordinating conjunction:
But the deeper truth is that free will doesn’t even correspond to any subjective fact about us – and introspection soon proves as hostile to the idea as the laws of physics are. (page 6)
So, when thinking about how the ideas expressed in your sentences are related, keep in mind exactly what you want to say and use the appropriate conjunction and punctuation. You may join two clauses into a sentence using a conjunction. But you may keep them separate.