The traditional understanding of grammar—the one we associate with the prescriptivist position—began in ancient Greece and Rome. For hundreds of years, grammar was synonymous with the study of Greek and Latin. These languages were regarded as perfect—or nearly so—and their grammatical structures were taken to be universal forms by which all "vulgar" languages should be judged. It was not until the seventeenth century that writers began to turn their attention systematically to the grammar of English itself, and when they did so, they applied the structures that they had learned studying classical languages to English.
English, of course, differs greatly from Latin, and the grammatical categories developed to describe Latin did not always fit perfectly with English. How the early English grammarians reacted to these difficulties depended on the individual inclination and aptitude of the writers, but most tended to assume that when the two languages differed, it was English that was corrupt and in need of reform.
The grammarians who shaped traditional English grammar were largely amateurs, people of no particular training, qualified chiefly by their interest in the subject. Some had a strong intuitive understanding of their subject; others were little more than hacks. They bequeathed later generations a mixed heritage. On the one hand, linguists continue to use much of their terminology, although they have refined many details. On the other hand, the emphasis on the perfectibility of language encouraged a severity towards the day-to-day language of many people that can still be seen in many writing handbooks and in the way many people view language errors.
Traditional definitions of grammar do not vary much. Samuel Kirkham, author of one of the best-selling grammar books in nineteenth-century America, defines grammar as "the art of speaking and writing the English language with propriety"
The first thing to notice is that grammar is seen as an art. In other words, the overriding goal of traditional grammar is to produce aesthetically pleasing English. Traditional grammar doesn't try to explain the most basic aspects of language—the point at which linguistics begins. It takes the basics for granted. Traditional grammar is not about speaking any old form of English, but one particular form—a proper one.
Kirkham's word "propriety" suggests that grammar is a form of social decorum and therefore that grammar involves following rules. And so, as even cursory thought will show, language must. Without some agreement as to the rules, there could be no communication. But just what do we mean by a rule?
The rules in traditional grammar books comprise a list of dos and don'ts: make subjects agree with verbs, don't split infinitives, don't end a sentence with a preposition, and so on. Notably, many of these rules are regularly violated by native speakers. Traditional grammar books spend little time with rules such as "put adjectives before nouns." And they would never think to explain the ungrammaticality of a sentence like
(2) *The boss would like to may see you immediately.
Native speakers never make mistakes with such structures, and so traditional grammar books ignore them. The lists of rules do not so much explain how a sentence of English is put together as constrain what is permissible. As an unfortunate consequence of this approach, traditional rules form a semi-random collection of scattered bits of information, presented without system. And anyone who has ever tried to memorize lists of unconnected information knows how hard it is to retain all that trivia.
Linguists, like the writers of prescriptive grammar books, also assume that language is rule governed. When linguists speak of grammatical rules, however, they generally mean something different. To a linguist, grammatical rules mean one of two things. First, grammar can signify the internal, largely unconscious system that we use to combine sounds into words and words into larger meaningful units. Native speakers learn most of this system intuitively, without explicit training, when they acquire the language as children. To learn a language this way involves a tacit knowledge of grammar distinct from knowledge about grammar. Knowledge about grammar implies an explicit understanding of these normally unconscious processes. This explicit knowledge is not a natural process and is the subject of this course. When people say "I don't know any grammar," what they really mean is that they lack conscious knowledge about grammar.
Because these rules are inside our minds, they are not directly accessible to study. We cannot peer inside someone's skull to observe words being combined into sentences. So in addition to grammar as an internal system, linguists also use the term grammatical rule to refer to a formal mechanism that tries to explain how language is generated. Sometimes these rules are even presented in the form of equations using a quasi-algebraic notation.
In many ways, these rules are analogous to equations in other sciences, since they provide a formal description of something that happens. Also as in other sciences, these rules are hypotheses about the way language works. In other words, they make predictions about future actions that we can test. If the hypothesis doesn't match the observed results, it needs to be revised or abandoned. In a similar way, an equation of motion in physics lets us both describe what we have already seen—the path of a flying arrow, for example—and predict the path that future arrows will take.
The analogy to laws of physics is not perfect, though. For one thing, the rules of language are not immutable. Every language has its own set of rules, and these rules change over time, which explains why Shakespeare's language seems very different from our own. Gravitation does not work differently in France than it does in the United States, nor did objects fall differently after Galileo refuted Aristotle's old theory. Unlike physical laws, you can violate rules of grammar, although with some loss of intelligibility.
(3) *Her slept the bed until 10 o'clock.
No native speaker of English would consider sentence (3) to be well-formed. Clearly it violates some basic grammatical rules. But we can imagine someone—say a non-native speaker—uttering it, and we can figure out what is intended with a little more work than normal. But just try to violate the law of gravity!
It's important to remember that linguistic rules are formal abstractions. That is, by referring to a rule, we are not claiming that anyone is consciously applying it to produce language. We don't even need to assume that the rules are the unconscious steps that the brain performs when putting together language, although linguists would obviously like to know just what those steps are. Rules create a model that can be studied. Similarly, when we say a projectile follows a path, we mean we can describe where it goes, not that it chooses a particular course, or solves an equation in order to tell where to go next.
If linguistic rules resemble scientific equations, traditional prescriptive rules resemble table manners. You can eat your food perfectly well if you put your elbows on the table or chew with your mouth open. Many people do so all their lives. But if you want to join the local country club, watch out. Certain social circles expect you to follow the rules for table etiquette, and may exclude you if you violate them. Likewise, if you break prescriptive rules of language use, you will still be understood, but some may put you down as uneducated.
Like table manners, prescriptive rules are imposed by an outside authority. Traditional grammar puts great stock in authorities. Something is right or wrong because a book or a teacher tells us so. But who gets to decide? Some countries have a central body, such as the Academie Française in France, which pronounces on disputed issues. Whether such academies have any influence on actual language use is doubtful, but in any event neither the United States nor any other English-speaking country has such a group. Instead, prescriptions about grammar are made by "arbiters of usage." This group is not an organized body; rather it consists of anyone in a position to influence how other people use language: authors, editors, journalists such as William Saffire, writers of grammar textbooks and dictionaries. But those who have perhaps the greatest influence on the general public are classroom teachers. They are the ones who enforce the rules they believe are important when they correct student writing and speech. Even people who claim they don't remember, or never learned, any grammar in school can usually recall teachers with grammatical pet peeves who consistently criticized students for violating some rule or other.
Given the heterogeneous nature of this group, pronouncements on English usage vary widely from one another. Read any two usage manuals and you will likely find they contradict each other in many places. If you think about it, that's an odd situation. Prescriptive grammar begins with the assumption that there is a single standard form of the language which is correct. Why then can't the supposed experts agree? We're entitled to ask what criteria these authorities use to pass their own judgments. One purpose of this book is to equip you with the necessary tools to make your own judgments about issues involving language.
 The earliest grammarians were Greek, and Latin grammars were first developed in antiquity following Greek models. But in Western Europe, from the Middle Ages through the Renaissance, practically all educated people understood Latin but very few knew any Greek. Latin, therefore, had a much greater influence than Greek in the development of English grammatical teaching.
 Samuel Kirkham, English Grammar in Familiar Lectures, 12th ed. 1829.
 By convention an asterisk marks a sentence that is descriptively ungrammatical, that is, which native speakers intuitively judge to be unacceptable.
 Aristotle had claimed that a heavier object would fall faster than a light one. Galileo showed that they fell at the same speed, although not—as legend has it—by dropping anything off the Leaning Tower of Pisa.