If you participate in writing discussion boards of any kind, you’ll often see a novice writer ask a question about some rule of English grammar or style, which leads to a huge debate among the pros. One of the LinkedIn writing groups I belong to has been discussing the serial comma for over 3 months!
English does have a lot of firm rules, mainly relating to punctuation, grammar (subject and verb should match, don’t change verb tenses in the middle of a sentence, always use a determiner with a noun); and syntax (adjective goes before noun, modifiers should go as close as possible to the noun or verb they modify). All of these exist as rules because when the rule isn’t observed, the meaning changes or becomes unclear or is grammatically incorrect.
But what if you encounter a “rule” that writing professionals can’t agree on? Then the disagreement itself is proof that, in fact, no hard and fast rule exists about the question, no matter how hard any self-appointed grammar police may insist otherwise. Should you use the third comma in a series of words or phrases? (Some people say “always,” some say “never,” and some say, “It depends; does the sentence need the third comma for clarity?”) Can you use “then” by itself as a conjunction, or do you have to say “and then”? (Go with which ever looks better, sounds better, or makes the text lay out better on the page.) Is it wrong to end a sentence with a preposition? (A moment ago, I ended a clause with one, which comes to the same thing, but I’d bet no grammar police will notice, since it’s not the last word in the sentence.)
Often, these debates crop up where the language itself is changing. Many people no longer use the apostrophe to distinguish between “it is” and “it owns.” They just write “it’s” all the time. Many people also use lay and lie indiscriminately, to mean the same thing. These are distinctions that I continue to make for myself because they’re hard-wired into my writing brain. However, I no longer point them out to other writers as errors, because English has evolved in my lifetime to the point that Webster now recognizes both new usages as correct.
So what’s a professional writer to do, if you’re not sure which “rule” is correct? If in doubt, there’s only one hard and fast rule: you follow the usage preferred by the editors who hired you. They are the only grammar police who matter for the job at hand. If they don’t have a preference, choose your own preferred usage, and use it consistently.