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Transformational grammar

[This article concentrates heavily on Chomsky and Chomsky-related aspects of this topic. This is justifiable to some degree considering his importance in the field, but it would be nice to have a more balanced view.]
Transformational grammar is a broad term describing grammars (almost exclusively those of natural languages) which have been developed in a Chomskyan tradition. The term is usually synonymous with the slightly more specific transformational-generative grammar.

Deep Structure and Surface Structure

In the 1950s and 1960s, Chomsky developed the idea that each sentence in a language has two levels of representation - a Deep Structure and a Surface Structure. The deep structure was a direct representation of the semantics of a sentence, and was mapped onto the surface structure (which followed the phonological form of the sentence very closely) via transformations. There is a common misunderstanding that Deep Structure was supposed to be identical across all languages (thus creating a Universal Grammar), but Chomsky did not in fact suggest this in so many words. However, Chomsky did believe that there would be considerable similarities between the Deep Structures of different languages, and that these structures would reveal properties common to all languages which were concealed by their Surface Structures. It is arguable that the overriding motivation for the introduction of transformations was simply to make grammars more (mathematically) powerful, rather than to explain the origin of syntactic variations between languages. Though the ability of a grammatical theory to generalize across languages is fundamental to its worth in Chomsky's view, some of the definitive literature on early transformational grammar (e.g. Chomsky's Aspects of the Theory of Syntax, 1965) emphasizes the role of transformations in obtaining the necessary level of mathematical power in the syntactic component of a grammar, which, in his opinion, the structuralist grammars popular at the time did not have. Chomsky also emphasizes the importance of modern formal mathematical devices in the development of grammatical theory:

But the fundamental reason for [the] inadequacy of traditional grammars is a more technical one. Although it was well understood that linguistic processes are in some sense "creative", the technical devices for expressing a system of recursive processes were simply not available until much more recently. In fact, a real understanding of how a language can (in Humboldt's words) "make infinite use of finite means" has developed only within the last thirty years, in the course of studies in the foundations of mathematics. (Aspects of the Theory of Syntax, p8)

Development of Basic Concepts

Though transformations continue to be important in Chomsky's current theories, he has now abandoned the original notion of Deep Structure and Surface Structure. Initially, two additional levels of representation were introduced (LF - Logical Form, and PF - Phonetic Form), and then in the 1990s Chomsky sketched out a new program of research known as Minimalism, in which Deep Structure and Surface Structure no longer featured and PF and LF remained as the only levels of representation.

To complicate the understanding of the development of Chomsky's theories, the precise meanings of Deep Structure and Surface Structure have changed over time - by the 1970s, the two were normally referred to simply as D-Structure and S-Structure, and D-Structure bore increasingly less resemblance to the Deep Structure of the 1960s. In particular, the idea that the meaning of a sentence was determined by its Deep Structure was dropped when LF took over this role.

Innate Linguistic Knowledge

Terms such as "transformation" can give the impression that theories of transformational generative grammar are intended as a model for the processes through which the human mind constructs and understands sentences. Chomsky is clear that this is not in fact the case: a generative grammar models only the knowledge which underlies the human ability to speak and understand. One of the most important of Chomsky's ideas is that most of this knowledge is innate, and that all languages conform to a set of principles, while differing only in the values of certain parameters (and of course raw vocabulary). Therefore, a baby can have a large number of expectations about the structure of language in general, and need only deduce the values of the various parameters for the language(s) it is learning. Chomsky was not the first person to suggest that all languages had certain fundamental things in common (he quotes philosophers writing several centuries ago who had the same basic idea), but he helped to make the innateness theory fashionable after a period dominated by more behaviorist attitudes towards language. Perhaps more significantly, he made concrete and technically sophisticated proposals about the structure of language, and made important decisions about how the quality of any given theory of grammar should be evaluated.

Chomsky goes so far as to suggest that a baby need not learn any actual rules specific to a particular language at all. Instead, all languages are presumed to follow the same set of rules, but the effects of these rules and the interactions between them can vary greatly depending on the values of certain universal linguistic parameters. This is a very strong assumption, and is one of the more subtle ways in which Chomsky's current theory of language differs from most others.

Grammar theories

In the 1960s, Chomsky introduced two central ideas relavent to the construction and evaluation of theories of grammar. The first was the distinction between competence and performance. Chomsky noted the obvious fact that people, when speaking in the real world, often make linguistic errors (e.g. starting a sentence and then abandoning it midway through). He argued that these errors in linguistic performance were irrelevant to the study of linguistic competence (the knowledge which allows people to construct and understand grammatical sentences); according to this argument, the linguist can study an idealised version of the language, greatly simplifying linguistic analysis. The second idea related directly to the evaluation of theories of grammar. Chomsky made a distinction between grammars which achieved descriptive adequacy and those which went further and achieved explanatory adequacy. A descriptively adequate grammar for a particular language defines the (infinite) set of grammatical sentences in that language, whereas a grammar which achieves explanatory adequacy gives an insight into the universal properties of language which result from the innate linguistic structures in the human mind. Therefore, if a grammar has explanatory adequacy, it must be able to explain the various grammatical nuances of the languages of the world as relatively minor variations in the universal pattern of human language. Chomsky argued that, even though linguists were still a long way from constructing descriptively adequate grammars, progress in terms of descriptive adequacy would only come if linguists held explanatory adequacy as their goal. In other words, real insight into the structure of individual languges could only be gained through the comparative study of a wide range of languages.


Chomsky went against the prevailing viewpoint amongst linguists in the first half of the 20th Century by suggesting that the notions "grammatical" and "ungrammatical" could be defined in a meaningful and useful way. An extreme behaviorist linguist would argue that language can only be studied through recordings or transcriptions of actual speech, the role of the linguist being to look for patterns in such observed speech, but not to hypothesise about why such patterns might occur, nor to label particular utterances as either "grammatical" or "ungrammatical". Chomsky argued that the intuition of a native speaker is enough to define the grammaticalness of a sentence; that is, if a native English speaker finds it difficult or impossible to understand a particular string of English words, it can be said that the string of words is ungrammatical [1]. This concept freed linguists from studying language through a corpus of observed speech, since they were now able to study the grammatical properties of contrived sentences. Without this change in philosophy, the construction of generative grammars would have been almost impossible, since it is often the relatively obscure and rarely-used features of a language which give linguists clues about its structure, and it is very difficult to find good examples of such features in everyday speech.

Mathematical Representation

Returning to the more general mathematical notion of a grammar, an important feature of all transformational grammars is that they are more powerful than context free grammars. This idea was formalized by Chomsky in the Chomsky hierarchy. It is now generally accepted that it is impossible to describe the structure of natural languages using context free grammars (at least if these descriptions are to be judged on vaguely Chomskyan criteria).


Some of the rules of Transformational-Generative Grammar are quite simple, such as the Head Initial/Final rules:

Most languages tend to favor only one of these structures (there are exceptions). Japanese is a Head Final language, whereas English is a Head Initial language. Slightly more languages are Head Final.

Other rules are more complex, such as the so-called "Wh-Question Formation Rule" for English, which can be summarized as:

1. Begin with a simple declarative, with a missing item:

2. Insert the appropriate Wh-word for the expected lexical category of the answer: 3. Change the form of the verb to the appropriate "did X" construction: 4. Use Subject-Auxiliary Inversion to form an interrogative: 5. Move the Wh-word element to the front of the sentence: While Chomsky and others have abandoned much of traditional TGG (the mechanisms described in the example above have been out of date since the late 1960s), it continues to have useful applications in syntactic analysis and the study of children's language acquisition.

See also: linguistics, grammar, syntax, semantics

[1] This is not entirely true; it is possible for a sentence to be both grammatical and meaningless, as in Chomsky's famous example "colourless green ideas sleep furiously". Such sentences are nonsensical in a very different way to (non-)sentences like "man the bit dog the".