[Originally published on Facebook 2015-09-12.] When I was a child I was taught that when conversing in French with any of my adult Belgian relatives I had to use the plural form “vous” when addressing them (rather than the singular “tu”) since the plural form has to be used in formal contexts. Not many people realise this, but English had the same rule. The second person singular is “thou” and the plural is “you”. The plural form was used in formal contexts. Prayer books used the informal singular form to denote the closeness encouraged by instructions such as “call God Father” and the symbolic tearing of the temple veil.
Living languages have an interesting fluidity. They evolve with the people who continually use them. The English language is often criticised for its many exceptions to rules. Some of this is caused by the blending of the different languages that have contributed to its evolution, but some of it comes from so many people breaking a rule that the broken rule becomes standard. (How many use “awful” to mean “full of awe”?) Over time, people began to use the formal “you” in increasingly informal contexts to the point where “thou” was considered old-fashioned. Additionally, its retention in prayer books and the change in attitudes towards religion made “thou” seem stuffy and formal.
This use of the plural form in singular contexts to indicate formality can also be seen in the so-called “royal we”. When the Queen addresses the nation, she refers to herself in a formal context using the plural “we”. Over the past decade or so, more and more non-fiction writers are using the plural third person “they” in a singular context. This is done to avoid the reference to gender and has attracted some criticism from people who feel it’s breaking the language rules, but it actually follows the old linguistic tradition of using the plural instead of the singular in a formal context. So, if you abhor the use of “they” in a singular context, perhaps thou shouldst consider thy use of “you” when addressing only one individual.