This is a question every writer has once and then. Whenever discussions arise about style and grammar, someone is always going to ask the decisive question: Based on what authority do you maintain that this is an error?
Leaving aside what we all would identify as “errors”, this is an important question. There are conventional uses we all learn in school and high school that we associate to a proper use of written English.
We commonly recognize a typo or misspelling and severe grammar misuses. But when we leave the obvious it can get tricky. Tricky, because there is not superior instance that defines right and wrong in an ultimative way.
In a world where everything is based more and more on defined rules, ranging from the size and weight of toilet paper in the EU to the exact measure for quality classification of bananas for export, grammar and orthographic rules are like islands of arbitrary usage in a sea of rules and exceptions to these rules.
There is no ICANN, WW3, IRS or NASA protocol for the use of language. But there are tons of tools that use rules to define and therefore somehow decide about the proper use of the English language.
And there are lots of places where the English language is spoken and written quite different to other places. British English, American English, European English, Canadian English, Australian English or English in African countries have different spelling rules.
Who rules then? Is there any historical right to define the grammar rules by Britain? Or is there a political weight imposing its rules by the US? Not really.
However, there are some institutions with enough moral authority and corporate power to establish some sort of rule set we commonly accept as “right”. This set of rules is the basis for all common spellcheckers, human copywriters and proofreaders, teachers and universities.
Some of them have more prestige and therefore more weight in their rule sets, like the Oxford Dictionary people, Harvard University or just the Stylebooks and Publication guidelines of the most powerful editors and press journals.
As in many languages with European origins, rules came with history and developed mostly along the development of print.
English grammar and spelling rules came by necessity: With lots of regional dialects and people unable to understand each other beyond their little marks and boundaries, when printed books were invented, the communication process needed some standardization.
Therefore the first printed grammar books we know of date from the renaissance era. This was a trend not only in medieval Britain but also in the rest of Europe.
As always, those who have the power define the rules. Therefore what we would today define as correct British English is in fact what was established around London and the surrounding Midlands. The prestige and power of Oxford and Cambridge as knowledge centers brought us the modern standard written English.
If politics had been different, proper English would have adopted the Scottish, Welsh or Irish usage and be taught and spoken in a quite different way today. However, no one installed any official Language Academy. The result is that English grammar is a set of rules that many people have agreed upon, but there is no ruling institution.
And this leads to a pragmatic and effective use of grammar. Therefore there is a great tolerance and permeability for new vocabulary and integration of spoken elements into the commonly accepted usage.
We should be glad for this. Language is a living entity based on crowdsourcing on a higher level. It should keep that way.
Proper grammar is decided by usage within a community. You notice this when you see the different spellcheckers in your text editors for British, American, South African, Indian, Caribbean English or any other regional form of English.