No topic in English usage has received more attention in modern practice than the lack of a common-sex singular personal pronoun. For most of the language’s history, he dealt with all such matters: He who is anyone knows me, The student must complete his test, Let no one leave without his pay. These phrases use obvious masculinity that, whether we want to admit it or not, ignores female involvement.
Unfortunately, English does not offer a clean common-sex pronoun. Our language has only three third-person singular pronouns: he, she, and it. Writers have suggested adding a common-sex pronoun like thon, heshe, hse, hu (human), per (person), himorher, ha, and shiz, but none of those have ever caught on. I have occasionally seen the abhorrent s/he, which has the sole effect of forcing readers to stumble over the slash and decide upon a preferred pronoun. Do not impose upon the reader the task of your expression.
Many writers want to use the colloquial they for the singular pronoun. Henry Fowler calls it horrible and Bryan A. Garner resigns to its popularity, but, as many a copyeditor and usage expert agrees, the use of they for he or she is grammatically wrong. At the expense of number, they risks confusion. The child went to the zoo and watched the penguins, and they clapped with great joy. To whom, if we accept they as singular, does they clapped refer? And if we accept they as singular, should verbs agree with the singular subject or the plural pronoun? The person must decide if they wants to listen is correct if they is a singular pronoun but sure doesn’t sound it. They does not solve the problem; it only introduces new ones.
The most popular alternative, he or she, may work in most situations, though overuse of he or she creates bloat, slows the reader, and can suggest two people are involved rather than one. The astute reader may also ask why we say he or she and not she or he, which reminds us of the original issue.
Where does that leave us? We could accept he and man to mean also the general human being—one of the definitions for man in the Oxford English Dictionary. But while he falls invisible to readers like myself, there are plenty for whom it causes great offense. Thus, my first suggestion when encountering the need for a common-sex pronoun, which echos most style guides, is to rewrite your prose to avoid relying on such a pronoun. Sometimes the singular can become plural, though plural feels less intimate: If the reader disagrees, he or she can shove off or If the readers disagree, they can shove off. Where the plural doesn’t work, consider rephrasing to avoid the situation altogether; the lazy writer may complain, but, as an example, I have removed singular third-person pronouns throughout my website’s articles, and no reader will complain.
But, alas, some situations require a lovely common-sex singular third-person pronoun. With the wrong choice (s/he, any of the thons or heshes), you call attention to the word itself and the politics behind it rather than the content you wish to discuss. Some writers switch he and she within a piece, but that also calls attention to the politics and, at worst, confuses the reader. But that shouldn’t stop you from switching up the pronouns between works: one essay, she, the next, he, and so on. It’s kind, gentle, and shows conscientiousness to both sides of our language’s most hotly-debated topic.