In our sentences, we sometimes include a condition before something can happen or be prevented from happening. This is called a conditional clause. (People you would never want to befriend call it the protasis.)
A conditional clause is an independent clause we have made dependent by adding a subordinating conjunction to the beginning:
If Phoebe’d been there,
A conditional clause usually begins with if. It can also begin with even if, because, unless, whether or not, provided that, as long as, although, when, and similar words and phrases that set up an event that must happen or fail to happen or even will happen despite the condition.
In an earlier Tip [The Best-Kept Writing Secret of All Time], I explained how we engage and move a reader forward by putting the supporting point at the beginning of a sentence and the important point—the word or phrase we want to emphasize—at the end. (Those same people you would never want to befriend call this important point the apodosis.) A conditional clause will almost always be the supporting point, and so it should appear at the beginning of the sentence to set the stage for what will arise because of, or despite, the condition. From The Catcher in the Rye:
If a girl looks swell when she meets you, who gives a damn if she’s late?
Note that when we put the condition at the beginning, we arrange our sentence chronologically, which helps to create flow in understanding, enhancing our reader’s comprehension. It’s a much crisper and more compelling way to express ourselves, and it puts the important point always at the end. A few more examples:
Owners now face losing their homes because they cannot afford the repairs.
Because they cannot afford the repairs, owners now face losing their homes.
I would not write “Mr.” or “Ms.,” unless I had to follow a company stylebook.
Unless I had to follow a company stylebook, I would not write “Mr.” or “Ms.”
Please let me know if you have any questions.
If you have any questions, please let me know.
Note to smart people concerned about whether to use was or were in a conditional clause beginning with if. We’re talking about—I hate to mention this term in polite company, but I will anyway—the subjunctive mood. Although Fowler wrote long ago, “The subjunctive is dying,” we still should know this: If our conditional clause begins with if and is contrary to fact, then we use were instead of was, even though our subject is singular. These two sentences from The Old Man and the Sea are correct:
If I were towing him behind there would be no question. Nor if the fish were in the skiff, with all dignity gone, there would be no question either.
I and fish are singular, but if they are part of a condition contrary to fact (which they are - no fish in the boat, no fish behind the boat), they require the subjunctive were. Hemingway uses no comma after the conditional clause ending with behind, but that’s Hemingway; the rest of us need a comma.
Often we mistakenly default to were when the condition only might exist:
If his shoulder were dislocated, he would never pitch again.
This is incorrect because we don’t know the condition of his shoulder, so it's not contrary to fact. Use was.
One last point about conditional clauses: Unless you’re a computer programmer, do not be concerned about “if-then” statements. We do not need then at the beginning of the clause following a clause that begins with if. Then may be implied. (Or you may put it in.) Professor Strunk wrote this sentence in The Elements of Style:
If a conjunction is inserted, the proper mark is a comma.
No then. But, as the professor demonstrates, we should use a comma to separate the conditional clause from the independent clause, Hemingway bedamned.