One of the most surprising discoveries of the past century was the reappearance of the Coelacanth, a lobe-finned fish that was thought to have died out millions of years ago. Scientists were astounded that a "living fossil" survived into modern times.

Well, the English language also has a "living fossil," a remnant of an ancient way of speaking that's survived--barely--into modern times. And like the Coelacanth, it may become extinct within the next few decades.

Before I explain the rule, here's a quick question. Are the following grammatically correct?

  • "I were rich."
  • "She leave now."
  • "He be guilty."

While they sound a bit odd and even caveman-ish while standing alone, when placed in context, they are entirely grammatical. Like so:

  • "If I were rich, I would buy a Ferrari."
  • "I insist that she leave now."
  • "Should he be guilty, he deserves punishment."

What you're looking at there are the last remnant of what was once a huge part of the English language: the Subjunctive Mood. It was (and is) a quick and convenient way to quickly communicate to listeners that you're talking about something that isn't real (yet).

In English, reality--what actually existed, exists or will exist--is communicated using something called "Indicative Mood." These are the verb forms that everybody uses uses every day. Like so:

  • "I am rich, so I'm buying a Ferrari."
  • "She is leaving now.
  • "He is guilty and will be punished.

By contrast, you use the Subjunctive Mood when you're discussing something that didn't exist, doesn't exist or might not exist in the future. In other words, if it's real, use the Indicative; if it's not, use the Subjunctive.

In more formal languages, the Subjunctive mood for a typical verb might several dozen forms (past, present, future, etc., first person, second person, third person, singular, plural, etc.), most of which are different from the same forms in the Indicative.

That's a lot to learn, as anyone who's taken a few years of Latin knows.

Ancient English had some of that complexity, but today all that's left are a few quirky idioms. And even they're starting to disappear.

For example, it's now much more common (in both senses of the word) for somebody to say "If I was rich..." (Indicative and incorrect) than "If I were rich..." (Subjunctive and correct). Similarly, most people would probably say "I insist that she leaves now" (Indicative and incorrect) rather than "I insist she leave now." (Subjunctive and correct). Same thing with "If he is guilty,..." (Indicative and incorrect) replacing "Should he be guilty,..." (Subjective and correct). 

While grammatical rules like this might seem a bit silly, they're cultural markers (for those who notice them) of whether a speaker is educated and articulate. It's a little like a secret handshake. Use the Subjunctive correctly and everyone who's "in the club" knows you're a member.

Lest this seem stuck up or arbitrary, almost everyone does the same thing when searching even further down the grammatical chain. Most people, for instance, downgrade speakers' intelligence should they use simplified forms of the Indicative Mood.

For example, "I is happy" rather than "I am happy" sounds backwoods and uncultured, even though it's really just a way to make English more consistent. "I is, You is, He is" is, in a way, more sensible than the standard "I am, You are, He is."

The Subjunctive Mood is just a more extreme case of the same cultural snobbishness that causes most people to look down on those who are simplifying the language even further.

Illogical though it, if you use the Subjunctive correctly, you'll sound smarter to people who pay attention to such things. Regardless of how smart you actually are.