conditional-constructionsgrammar-myths
I remember hearing that if and would should never be in the same sentence. I however don't know what is actually considered the same sentence, so here are to examples.
If he would only stop bothering me..
I'm assuming this is incorrect
It would have been better if I had the roof repaired yesterday rather than leaving it until today.
I'm assuming that this is actually correct, even though would and if are in the same sentence.
Is this correct?
Do English teachers no longer teach that this is a grammatically incorrect thing to do?
One day in first grade, in the United States, my teacher told the class that it's wrong to start a sentence with a conjunction. The example she used was "And". She gave a straightforward reason: since a conjunction joins two things, it doesn't make sense to start a sentence with one, since nothing has yet been said that could be joined to something else.*
A few minutes later, we came across a sentence in a book we were reading aloud from that started with "And". Someone pointed it out. The teacher explained, "Well, you can only do it if you're an author."
Lesson learned. The rule is fake.
I could open up the King James Bible to a random page and point out sentences that begin with "And". Anyone with access to Google Books or Google Ngram could beat you over the head with a thousand sentences starting with any conjunction you choose. I hope you would find that unconvincing. People violate subject-verb agreement all the time, it's easy to find examples in "corpora" of any grammatical violation you like—but that doesn't mean they aren't grammatical violations. I'd like to give you something genuinely convincing: an explanation of the grain of truth within the rule, and an explanation of why it makes grammatical sense to violate it.
First, let's look at the real basis of the rule.
When children are learning to write, they often don't understand the difference between a complete sentence and a sentence fragment. They don't understand yet that written language is not merely a transcription of speech, but a refined, more formal version of the language. In written language, we normally expect a sentence to express a proposition clearly: to affirm or deny a predicate of a subject. Conjunctions play a simple and straightforward role in this: they join elements of sentences together. "You can have cake and ice cream but not coffee or cigarettes."
As my first-grade teacher said, there is something odd about starting a sentence with a conjunction when there's nothing to join yet. When children are just learning to write, requiring them to use conjunctions only for their primary role as joiners of elements within sentences can be a useful, temporary constraint. Temporary constraint is a very effective teaching method for many skills: by focusing you on one way of doing something, you master it much more quickly than without the constraint; and when you release the constraint, you gain keen insight into the full range of what's really possible beyond it.
People who haven't mastered the strict use of conjunctions, or who don't know a sentence from a sentence fragment, often put conjunctions at the beginnings of sentences carelessly and sloppily, as in the examples you offered. Many real-life examples are much worse, of course. The authors of such writing haven't gathered and organized their thoughts in way that is suitable for clear writing. To a reader, it comes across as incoherent and careless. Much writing that starts a lot of its sentences with conjunctions is quite tiresome. Just have a look at YouTube comments or the Book of Mormon.
Another book I read when I was a little boy told a story about a princess who was looking for a husband. She rejected one of her suitors because he began every sentence with "I". That little tidbit teaches much wisdom! People who start every sentence with "I" quickly become tiresome. It's a thoughtless, inconsiderate, unempathic way of speaking.
But does that mean that starting a sentence with "I" is ungrammatical? Of course not. Grammar is only the nuts and bolts of how words connect and inflect to make meaning. What you choose to mean is outside the scope of grammar.
Even though conjunctions at the start of sentences can be tiresome, they serve an important grammatical role there:
They join elements of discourse at a higher level than within a sentence.
When used at an opportune moment, to signal a reversal from a previous line of thought or to deny the expected outcome of a sequence of events just described, "But" at the beginning of a sentence can make clear, well-organized rhetoric. Upon seeing a sentence starting with "But", outside its usual role as signaler of an exception within a sentence, the reader understands that the new sentence as a whole will describe a reversal or exception to the preceding sentences.
"But" at the start of a sentence is most commonly useful to deny an expectation that arose from several preceding sentences, or to introduce a compound sentence containing several exceptions, but of course that can't be a rule. When to use it is a rhetorical choice, subject simultaneously to all the considerations of rhetoric. Its grammatical role, as joiner and organizer at a higher level than within a sentence, is straightforward.
* Obviously, that only applies to coordinating conjunctions, not subordinating conjunctions. Let's not split hairs.
In reported speech, we backshift the tense of verbs.
she said "I am ready"
she said that she was ready.
It is called reported speech because it probably occurs most often with the verb "say*, as in my example, but it is actually used with a whole lot more verbs. There are a lot of verbs in that list: sense isn't among them, but it should be there. In this context, sense means feel, which is in the list.
We use present perfect I have XXXed to talk about something that was started in the past and is not yet completed: once I have XXXed refers to what's going to happen when it is completed in the future. In reported speech, once I have XXXed backshifts to past perfect once she had XXXed.
She said "Once I have painted my bedroom...."
She said that, once she had painted her bedroom....
We use backshift with sense: your sentence uses past perfect. Both simple past and present perfect backshift to past perfect, so we need to decide which was meant:
he sensed that once he had finished, he would feel better. - backshifted
he sensed "once I finished, I will feel better". - simple past
he sensed "once I have finished, I will feel better. - present perfect
It's not difficult to work out that the correct reverse-backshift is present perfect.
Best Answer
As everybody so far has told you, this “rule” is quite false. FumbleFingers, J.R. and Matt have given you quite enough counterexamples to prove that.
But it appears that yours is not an isolated misunderstanding. On Google I’ve found half a dozen instances of other students who “remember being told this in school”; it’s enshrined in a mnemonic rhyme: IF and WOULD aren't good, IF and WILL make me ill; and there’s at least one website for english learners, speakspeak, maintained by a man who “has been teaching English for 20 years”, which explicitly prohibits sentences of the same form FumbleFingers endorses. So the interesting question is Where would such an absurd rule come from?
I suspect that this is what I have elsewhere called a “baby rule”, an overgeneralization designed to protect learners from some very common mistake before they know enough English to recognize when the rule is no longer valid.
In this case the reason for the rule is fairly clear. In the first place, its scope is not a sentence but a clause; if you look at speakspeak you will see that the author says that the error is “putting ‘would’ in the if-clause”. And many of the examples there are in fact instances where if … will/would is unidiomatic:
It is quite true that English does not employ will/would in condition clauses in a futurive sense.
This is difficult for speakers of some other languages with different syntax. Indeed, one of the ungrammatical sentences at speakspeak is difficult for many native speakers; it is the parade example of what the British, with more accuracy than charity, characterize as “footballer English”, because it is characteristic of athletes-turned-broadcasters, who are anxious about their colloquial speech and prone to hypercorrection:
Where the rule breaks down is in precisely the sort of sentence which FumbleFingers offers. Speakspeak is quite wrong in holding these sentences to be ungrammatical:
The wills and woulds in these sentences, and Fumblefingers’, are not futurive but are representatives of the now obsolete volitive sense of will. In these uses, will originally signified, approximately, be willing or consent:
The volitive sense is no longer present in such expressions as these; but because they were not futurive, the form endured and became fossilized in them.