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Lecture 2 Modals of Generative Grammars Intuitively, what the internalized grammar does is to mediate between sound (i.e. what one hears, and alternatively what one produces) and meaning (i.e. what one understands, and alternatively what one wants to communicate) (cf. A.Cornilescu). Thus, each sentence must be associated with a semantic interpretation and with a phonological interpretation. Chomsky's early model of GG devised in "Aspects" (1965) contained, in a simplified version, a tripartite structure: The Semantic Component The Syntactic Component The Phonological Component In this conception, syntax is responsible for "producing" the grammatical sentences of language; these sentences are assigned a semantic interpretation (a meaning) in the Semantic Component and they are also given a phonological interpretation in the Phonological Component. The Syntactic Component occupies a central position. To quote Chomsky again, "it became increasingly clear to me that limitation to procedures based on substitution, matching, and similar "taxonomic" operations was arbitrary and unwarranted. One might approach the problem of projecting a corpus to a language of grammatical sentences in an entirely different way, with a procedure for evaluating a completed system of categories rather than a procedure for constructing these categories step by step by taxonomic methods" (Chomsky (1975) (Reflections on Language)). Thus, gradually Chomsky arrived at the conclusion that "grammar is a system of rules that specifies the set of sentences of some language L, and assigns to each sentence a structural description. The structural description of a sentence S constitutes a full account of the elements of S and their organization" (Chomsky, (1975), ‘Reflections on Language’)). The idea of constructing a grammar as a system of rules leads to the fundamental epistemological problem of justifying this construction that is of validating linguistic research in general. To validate linguistics as the science of language, Chomsky put forth the concept of 'linguistic theory' (LT). As will appear, LT is in fact a universal grammar, although the term itself is not yet used (in ‘Logical Structure of Linguistic Theory’, 1955/1975). Thus, we have to do with the following triplet: Linguistic Theory (LT) -- Grammar (G) -- Language (Lg). LT defines a system of levels of representation. The levels considered in LSLT are the following, reflecting the passage from structuralism to Generative Grammar: phonetic (words are made up of phonemes), word, lexical category (Noun, Verb), morphemic (there are lexical morphemes such as table and grammatical morphemes such as the marker of plural -s in tables), phrase-structure and transformational. The use of "Generative Grammar" should not be misleading: "generative" means that the description is rigorous and explicit."When we speak of the linguist's grammar as a "generative grammar" we mean only that it is sufficiently explicit to determine how sentences of the language are in fact characterized by the grammar"(i.e. they conform to the assumed grammar) (Chomsky (1980), ‘Rules and Representations’). So, the term "generative" is not used as a synonym for "productive" but for "explicit and formal". The motivation behind the level construction has to do with the complexity of language. Thus, if one were to give a direct description of the set of grammatical sentences of L as a sequence of phonemes, one would be faced with an unmanageable task. Instead of attempting this, the linguist analyses phoneme sequences into morphemes, morphemes into sequences of words and then phrases (NP,VP). The term of UG, competence and performance have not been introduced yet in LSLT. However, from among the problems that have constantly concerned Chomsky it was especially the problem of rule-governed creativity: "The primary question for LT is to show how speakers produce and understand new sentences" (Chomsky (1975), Reflections on Language)) and also "The fundamental long-term task is to provide an explanation for the general process of projection by which speakers extend their limited linguistic experience to new and immediately accepted sentences" (Chomsky (1975)). The idea of constructing a grammar as a system of rules leads to the fundamental problem of evaluating rival descriptions, selecting among them on a principled basis. That is why a linguistic theory was needed. Linguistic theory does offer an evaluation procedure for grammars as it provides two types of evaluation criteria. There is first the criterion of external adequacy or descriptive adequacy. A grammar is externally or descriptively adequate if it is "faithful to the data", that is, if it produces all and only the correct sentences of the language. It is not enough for a grammar to define the set of well-formed sentences of a language; it must also assign a structural description to each well-formed sentence. A grammar that claims that the structure of the English NP is always Det + N, without specifying what kind of noun may follow the determiners is descriptively inadequate since it may come up with sentences like: *The Jane is here, *Some London is in England. A theory of grammar must operate within the constraints on the form or function of a language. Obviously, the relationship between individual grammars and the general theory is a complex one. The discovery that the grammar of a language has a rule-type that is not compatible with the theory of grammar may entail that the theory has to be modified in the relevant respects. On the other hand, it may turn out that a more careful analysis of the data from the language in question yields a solution involving the interaction of two already familiar rule-types so that no adjustment of the overall theory is necessary. In general, the ultimate objective should be an overall theory which is as restrictive as possible in terms of the descriptive apparatus it endorses while remaining compatible with the set of data it purports to account for. Such a restrictive theory is an empirical theory because it makes testable predictions about what is a possible natural-language grammar. Secondly, there is the criterion of internal adequacy or explanatory adequacy. This requirement means that a grammar should conform to the theory of grammar, it should obey the formal requirements stipulated there, it should meet conditions of simplicity, it should offer intuitively satisfactory explanations. Only those descriptively adequate grammars that are compatible with its requirements will be genuinely adequate. A theory of this general sort constitutes an explanation of why it is that the grammars of natural languages are set up in the way they are. Such a theory explains "why it is that from the indefinitely large range of logically conceivable types of rule of principle only a handful are ever exploited in the grammars of human languages" (Horrocks (1987)). By contrast, a theory that excludes nothing as impossible can, in turn, explain nothing. A theory that selects the best available descriptively adequate grammar for a given language is said to be explanatorily adequate. As said above, in "Aspects of the Theory of Syntax" (1965), Chomsky introduced the fundamental conceptual pair 'competence' (tacit linguistic knowledge of the speaker) and 'performance' (actual use of the language by the speaker). He will also explicitly refer to '"universal grammar", a term which supplants "linguistic theory", and to the conceptual triad 'universal grammar (UG) -- grammar of a particular language (G) -- language (Lg). A theory of grammar that enjoys both descriptive and explanatory adequacy is in effect a theory of universal grammar defining the descriptive resources available for constructing the grammars of individual languages. The more powerful such a theory is, the less comprehensive the grammars of particular languages will be: that is because, to a very large extent, the properties of the rule-systems that make up natural language grammars will be automatic consequences of the theory of universal grammar. It is therefore natural that the emphasis will shift from issues of descriptive adequacy to issues of explanatory adequacy resulting in the discovery of quite abstract principles of considerable explanatory power. The UG theory, conceived in this way, also has the very desirable property that proposals or changes in one area have implications elsewhere. It is thus predicted that certain sets of grammatical properties will typically co-occur. In "Reflections on Language" (1975) and "Rules and Representations" (Chomsky (1980)) the pair UG --G will also be given a biological interpretation in terms of the pair "genotype -- phenotype". Language is not acquired in the same way as geography or learning how to ride a bicycle are learned. Language is part of the human inheritance; it is in our genes. "The physical basis of UG means that it is part of the human genetic inheritance, a part of biology" (Cook and Newson, 1996). "Universal Grammar is part of the genotype specifying one aspect of the initial state of the human mind and brain" (Chomsky (1980), Rules and Representations). Tied in with the genotype, the phenotype is defined as the properties of an organism that are produced by the interaction of the genotype and the environment. We have seen that it is the concept of "competence" which is fundamental for understanding Chomsky's views. The conception of grammars as models of competence signified a shift of focus from the investigation of linguistic behaviour to the study of the states of the mind which makes the linguistic study possible. Thus the three fundamental questions for linguistics, as stated by Chomsky in "Knowledge of Language", are the following: 1. What constitutes knowledge of language? (The prime duty of the linguist is to describe what people know when they know a language: English, French, Romanian etc. The answer to this question, in fact, involves the elaboration of a grammar) 2. How is knowledge of language acquired? (The second aim of the linguist is to discover how people acquire their knowledge of a language. Chomsky's answer to this is a rationalist theory of language acquisition based on the language faculty). 3. How is knowledge of language put to use? (A third aim would be to see how people use this acquired language knowledge. The answer to this question would involve a theory of communication). Chomsky's formulation of these questions reveals his preoccupation with the foundations of knowledge, his conviction that one can hardly understand the structure of the object/of the world, of the cogitatum, unless one has first understood the structure of the epistemic subject, the function of conscience, therefore, the cogito. Such an intellectual attitude relates Chomsky to Descartes (by whom he has been acknowledgedly influenced, see his "Cartesian Linguistics", 1966) Thus, Chomsky adopts the position of philosophical realism. To embrace a realist position means to claim that grammar is not a convenient fiction, but a reality of conscience, represented on the circuits of the brain. For Chomsky, linguistic research is developed within the frame of individual (cognitive) psychology. The main assumption is that the truly distinctive and most remarkable characteristic of the human species is the human cognitive capacity. The few remarks we have made on Chomsky's realist stance with respect to human cognitive capacity enable us to go back to the conceptual triplet UG--G--Lg, in the light of the refinements proposed in KL. UG is a theory of knowledge of language. UG theory maintains that the speaker knows a set of principles of maximal generality that apply to all languages. He also knows an array of parameters that vary within clearly defined limits from one language to another. UG theory aims at integrating language, mind and grammar. In the second chapter of "Knowledge of Language" entitled "Concepts of Language" a new distinction is put forth: that one between Externalized language (E-language) and Internalized language (I-language). E-language is language conceived as outside of conscience: "a construct understood independently of the properties of the mind/brain" (Chomsky, 1986 KL). E-language can be directly related with the notion of performance defined as " the actual use of language in concrete situations" (Chomsky (1965), Aspects of the Theory of Syntax). Such views of interpreting language have been and are still current. Bloomfield (1933) defined language as "the totality of utterances that can be made in a speech community". Under the same rubric, we may include the views of structural and descriptive linguistics and behaviourist psychology which tend to define language as a collection of actions or utterances, of linguistic forms (words, sentences), perhaps paired with meaning. Behavioural or sociolinguistic definitions of language, language as a social institution, as a set of normative practices also belong to understanding language as an Elanguage. If language is taken in this acceptance, the E-language is understood to be the linguist's real object of study; grammar is a derivative notion, a collection of descriptive statements concerning the E-language. "E-language, if it exists at all, is derivative, remote from mechanisms and of no particular empirical significance, perhaps none at all" (Chomsky (1991) "Linguistics and adjacent fields: a personal view"). Yet, as Cornilescu (1995) remarked, Chomsky might have been too hard on the notion of E-language; one should not forget that E-language is that factor of the natural world which triggers the development of I-language, through the subject's linguistic experience. Furthermore, although represented in the mind/brain, the grammar is not of the mind/brain; it is the grammar of an E-language produced under certain circumstances by the mind/brain. Thus, the grammar (the I-language) objectivizes itself in the E-language. The concept of E-language is contrasted in KL with that of I-language, defined as a "system of knowledge of language attained and internally represented in the mind/brain" (Chomsky, 1986, KL). Chomsky claims that the history of linguistics shows a shift from an E-language to an Ilanguage approach: "The shift of focus from the dubious concept of E-language to the significant notion of I-language was a crucial step in early generative grammar" (Chomsky (1991), Linguistics and adjacent fields: a personal view). A grammar, which is the study of I-language, describes the speaker's knowledge of the language and not the sentences he produces (i.e. E-language). "Linguistics is the study of I-language, and the basis for attaining this knowledge" (Chomsky (1987), Transformational Grammar: past, present and future). The similarity with the concept of "competence" is striking. Competence, defined as "the speaker's/hearer's knowledge of his language", is independent of situation. "By 'grammatical competence' I mean the cognitive state that encompasses all those aspects of form and meaning and their relation, which are properly assigned to the specific subsystem of the human mind that relates representations of form and meaning" (Chomsky (1980), Rules and Representations). The system of linguistic knowledge represented by I-language is constructed on the basis of the speaker's (child's) linguistic experience in terms of initial and final 'states' of the mind. The initial zero state or SO is the mind of the new-born baby who knows no language. At the end is the adult native speaker with full knowledge of the language, when competence is essentially complete. The adult native speaker's knowledge is called the steady state or SS. Chomsky takes the initial system of innate knowledge as represented by the universal grammar (UG). UG is the content of the initial state SO of the language faculty. "We take an I-language to be an instantion of the initial state" (Chomsky (1995), Language and Nature). Acquiring language means progressing from not having any language, SO, to having full competence, SS (cf.Cook and Newson (1996)). "A person proceeds from a genetically determined initial state SO through a sequence of stages S1, S2, …., finally arriving at a "steady state" SS which then seems to change only marginally " (Chomsky (1980), Rules and Representations) only, say, in the acquisition of new vocabulary items. The final stage SS consists of a core grammar, which incorporates the principles and parameters of UG and a mental lexicon. "UG is construed as the theory of human I-language, a system of conditions deriving from the human biological endowment that identifies the I-languages that are humanly accessible under normal conditions" (Chomsky (1986), KL). We conceive of I-language as modeled (at least in part) by the linguist's grammar (cf. Horrocks (1987), Cornilescu (1995)). I-language is the content of the so called "language state" SS attained by the cognitive faculty of language in a mature speaker. Despite appearances, Chomsky argues, E-language is a more arbitrary sort of object than I-language, harder to precisely locate in space or time. Moreover, an E-language is not a natural kind, the boundaries of the various E-languages are often arbitrarily fixed by means of socio-political decisions (e.g. Dutch and German (two languages) are much more similar than various dialects of Chinese (one language)). " We call Dutch a language and German a different language, but the variety of German spoken near the Dutch border can be understood by speakers of Dutch who live nearby, though not by speakers of German in more remote areas. The term "language" as used in ordinary discourse involves obscure sociopolitical and normative factors" (Chomsky (1988)). In contrast, I-language is in a sense more real and more clearly delimited through its very representation in the mind/brain. At the same time, this shift of focus is also, arguably, a shift towards the common sense, pre-theoretical notion of "knowing a language": to know a language does not mean to know a collection of utterances (E-language), but to know the way sound and meaning relate, therefore to know a grammar (including a lexicon) (cf. Cornilescu). Hence the conclusion that "the fundamental cognitive relation is knowing a grammar; knowing the language determined by it is derivative" (Chomsky (1975), Reflections on Language). Let us make the concept of UG more precise. One could ask the following not unrelated questions, to which we shall also suggest brief answers in Chomskyan terms: A. Why is it necessary to postulate the existence of UG and of the language faculty? B. What kind of object is UG? C. How do we decide what knowledge from the system of I-language is part of UG A. To find an answer to question A we might begin by examining where exactly is the real-world analogue of the linguist's general theory of grammar assumed to exist. Chomsky's answer is that, as a result of millions of years of evolution, human beings are endowed genetically with a faculty of language acquisition. The linguist's theory of UG is a model of this genetic endowment. The reason why one is brought to the postulation of UG and the language faculty is that this is the only way we can explain the creative use of language and especially the process of language acquisition. Chomsky underlies that the position of the linguist writing a grammar is somewhat similar to that of a child learning his native language. Both the child and the linguist are confronted with external data in the given language. The linguist's attempts to formulate the "rules" of the language and the child, as part of the natural process of growth, will ultimately construct a mental representation of the grammar of his language. In his efforts, the linguist is "helped along" by the formal framework offered by UG. A legitimate question to ask is whether there is anything that the child relies on, in learning his language and constructing a mental representation of the grammar of his language. In other words, is there any psychological counterpart of the linguist's UG, in the same way that the speaker's competence (internalized grammar) is the psychological counterpart of the linguist's grammar? Chomsky's strong claim is that the psychological counterpart of UG is the child's language faculty, which is itself a kind of universal grammar, a component of the child's mind, part of his genetic endowment. The child's mind is not, Chomsky believes, a "blank slate" when the child is born. Learning cannot simply proceed by analogy, induction and generalization. Chomsky radically departs from empirical theories of learning, embracing the view that the learning of a complex system like language would be impossible in the absence of some well-structured innate mental mechanism, which makes language acquisition possible. The child is thus innately equipped with a universal grammar. Chomsky's most powerful argument for innateness with respect to learning one's native language is, as mentioned above, the problem of the poverty of stimulus also known under the name of Plato's problem (Chomsky (1986), Knowledge of Language). The question, as formulated by Bertrand Russell, is this: "how comes it that human beings whose contacts with the world are brief and personal and limited are nevertheless able to know as much as they do know?" (Chomsky (1986), KL). Chomsky shows that native speakers have knowledge of grammatical principles that simply could not have been learned on the basis of generalization from samples of primary data. An example of the poverty of stimulus is the structure dependence of rules; the application of many rules depends on certain fairly abstract structures, and this fact prevents explanation or learning by mere induction or analogy. Here are some examples (due to Chomsky (1986), KL): (1) a. I wonder who [ the meni expected to see themi ] b. [ The meni expected to see themj ] (2) a. John ate an apple. b. John ate. c. John is too stubborn to talk to Bill. d. John is too stubborn to talk to. Both (1a) and (1b) include the clause marked by brackets but only in (1a) may the pronoun them be referentially dependent on the antecedent the men (to signal coreferentiality we coindex the two elements). However, in (1b) the pronoun them cannot be understood as referring to the men. The reference of the pronoun is determined by the situational or discourse context (and, consequently, the two elements bear different indices). Numerous facts of this sort are known without relevant experience that teaches us to differentiate between them. Yet, every child knows these things unerringly, and no pedagogical grammar ever draws the learner's attention to such facts. Turning to examples (2a) and (2b), sentence (2b) means that John ate something; this something is understood as arbitrary. This fact is explained on the basis of a simple induction: ate takes an object as in (2a). "John ate" may also simply mean "John dined". Yet, the same induction does not work in (2c) and (2d). Sentence (2d) does not mean that John is so stubborn that he (John) will not talk to some person, on the analogy with (2c), but it has the quite different meaning that John is so stubborn that some arbitrary person will not talk to him. Let us take another example analysed by Chomsky in "The Managua Lectures" (1988): (3) The man is at home Sentence (3) can be combined in a more complex structure such as (4): (4) The man, who is happy, is at home These are declarative sentences that make assertions (true or false, depending on the circumstances in which they are uttered). If we want to derive the interrogative sentence corresponding to sentence (3), we have to move the verb to the front of the sentences as in (5) below: (5) Is the man at home? Applying the same procedure to the more complex sentence (4), we obtain the ill-formed derived question (6): (6) *Is the man, who happy, is at home? Sentence (6) is for sure incorrect and the interrogative to (4) is not (6) but rather (7): (7) Is the man, who is happy, at home? The rule of question formation for complex sentences such as (4) is: look for the occurrence of is (and similar verbs), that is the main verb of the sentence, (the verb of its main clause), and place it in the front. This example is instructive in that it can be seen that no rule, which refers simply to the linear order of words, will work. Chomsky's comments on the fact that the rules of language ignore simple linear order but are structure dependent are gratifying indeed: "it is important to learn to be surprised by simple things - for example, by the fact that bodies fall down, not up, and that they fall at a certain rate; that if pushed, they move on a flat surface in a straight line, not a circle; and so on. The beginning of science is the recognition that the simplest phenomena of ordinary life raise quite serious problems: Why are they as they are, instead of some different way?" (Chomsky (1988)). Question formation of more complex structures is for sure "a simple but fairly dramatic case of Plato's problem" (Chomsky (1988)). Again, children never make errors about such matters and receive no training or reliable evidence about them. "If children are equipped with minds/brains that are designed to cope only with grammatical systems that have highly restricted properties, if, in other words, they are born with in-built knowledge of UG, the process of language learning will in fact be largely automatic and language-growth might be a more appropriate term. From this point of view the function of the primary data is not to provide the basis for learning the grammar of a language ex nihilo; it is simply to provide enough information for the in-built theory of universal grammar to be particularised to the grammar of the language of the speech community that the infant lives in" (Horrocks (1987)). The above types of examples, easily available in any language, allow the formulation of several important remarks: 1. the first characterizes the status of such knowledge as "knowledge without good reason or support by reliable procedures" (poverty of stimulus, or Plato's problem). 2. the second refers to the process of language learning. Children have to acquire a language from evidence they encounter; without any evidence, they will acquire nothing. Chomsky identified three logically possible types of evidence for acquisition: children learn from positive evidence (from actually occurring sequences in the language). The second type of evidence is 'direct negative evidence' (corrections by the speech community, which tests have proved to be of very little help, and thus it is not necessary for language acquisition). The third type of evidence is 'indirect negative evidence'; the fact that certain forms do not occur in the sentences the children hear may suffice to set a parameter, e.g. an English child, exposed to the data provided by the speaking community in which he lives will easily learn that English is a subject oriented language). The acquisition of the first language is better viewed as a process of maturation which takes place more or less without the conscious control of the subject. "We had no choice at all as to the language we acquired, it simply developed in our minds by virtue of our internal constitution and our environment" (Chomsky (1975), Reflections on Language). 3. thirdly, such examples also shed light on the kind of knowledge that can be supposed to derive from the principles of UG: on the assumption of uniformity of language capacity across the species, if a general principle is confirmed for a given language or for several languages and if, furthermore, there is reason to believe that it is not learned and surely not taught, then it is proper to postulate that the principle belongs to UG (cf. Cornilescu). Therefore, Chomsky's answer to the problem of how language is learned is that of a mental, biological a priori. "The study of language for Chomsky is an important way of investigating the structure of the mind and so ultimately of helping to advance knowledge to the point where a mind/brain distinction becomes unnecessary" (Horrocks (1987)). One of the faculties of mind common to the human species is the faculty of language. The faculty of language is an attribute that all people possess. It is indeed held to be specific to the human species; no other creatures apart from human beings possess a language organ. Chomsky assumes that language knowledge is independent of other aspects of mind. "We may usefully think of the language faculty, the number faculty, and others as 'mental organs', analogous to the heart or the visual system or the system of motor coordination and planning" (Chomsky (1980), Rules and Representations). In the absence of more definite evidence, the uniqueness of language principles (such as structure dependency) bears on an independent, autonomous area of the mind devoted to language knowledge. Language faculty is a separate compartment from other mental faculties such as mathematics, vision, logic, a.s.o. The conception of modularity of mind resembles the 19th century tradition of "faculty" psychology which also divided the mind into autonomous areas (Fodor, 1983). "UG is a theory only of the language module which has its own set of principles distinct from other modules and does not inter-relate with them" (Cook and Newson (1996), Chomsky's Universal Grammar). "The theory of language is simply that part of human psychology that is concerned with one particular "mental organ", the "human language", and "the study of language falls naturally within human biology" (Chomsky (1976), ‘Reflections on Language’). Thus, language faculty serves two basic functions: it provides a sensory system for the analysis of the linguistic data and a schematism (the innate UG) that determines a class of grammars, defining possible human languages. So, in a sense, Chomsky argues, with an acknowledged Platonic overtones, that it is not that we attain so much knowledge, but rather that we recover what was already known, activating this knowledge through experience. Given appropriate experience the language faculty passes from the state SO to the relatively steady SS , the state of knowing a particular language. UG is the theory of the content of SO ; particular grammars are theories of various I-languages that can be attained with SO fixed and, experience varying, each of them determining particular Elanguages. B. As to its status, UG (as content of SO ) is an ideal object which can be described as the set of conditions governing the possibility of the object (language) as well as any of its actualisations. UG is a genotype, a function mapping various courses of experience into particular phenotypes (particular) I-languages (grammars). C. The UG that the linguist postulates, (as a theory of SO) contains the set of principles and elements of any acquired system of linguistic knowledge. At the current stage in the evolution of GG--parametric grammar (or the "Government and Binding Theory", Chomsky (1981)), UG is described as a system of principles and parameters, which determine the general properties of representations of the assumed linguistic levels. What the linguist is seeking is a system of unifying principles that is fairly rich in deductive structure, but with parameters to be fixed by experience. The devices provided by UG must meet two conflicting requirements: 1. they must be rich enough descriptively to account for the attested variety of languages; 2. they must be sufficiently constrained and restrictive, so that to account for the acquisition of various languages on the basis of a limited evidence that leaves important problems underdetermined. As currently conceived, UG includes the following (among others): 1. general principles regarding the form of the grammar, first and foremost the specification of the assumed levels of representation. D - Structure ↓ S - Structure ↓ ↓ Logical Phonological form form UG also specifies the several modules (subtheories) that make up the grammar, among which we mention the following: a. X-bar theory, which is the study of the relations between a head element and a subordinate one; X-bar theory also defines a phrase structure grammar (Chomsky (1981), Emonds (1985). b. the modules of Binding Theory and Control Theory study the referential relations between various sorts of pronouns and their linguistic antecedents. The referential problems of examples (6) and (7) above would fall under Binding Theory. c. Case Theory studies the problem of how case is assigned to Noun Phrases. d. The Theory of Thematic Roles deals with the interpretation of Noun Phrases as arguments of predicates, function of such conceptual roles as Agent, Theme, Experiencer. UG also contains a set of concepts of high generality. These are the concepts that relate the various subcategories (e.g. 'government', 'binding', etc.). UG also includes a set of phonological features in terms of which the phonemes of various languages are constructed. And it also provides a set of syntactic features like ± Noun, ± Verb a.s.o., which underlie the definition of the lexical categories (Noun, Verb, Adjective, etc.) and grammatical categories (Noun Phrase [NP], Verb Phrase [VP], etc.) Within each subcategory there are general principles that belong to UG and which may define parameters, that is dimensions of variability across languages; learning a language is a matter of fixing those parameters in a certain way through experience. The theory is an interlocking arrangement of principles and sub-theories that interact in various ways. Moreover, in a theory of this kind, particular grammatical rules such as '"passive" or "question formation" are no longer treated and explained in isolation but represent the interaction of principles and particular parameter settings. The important thing is that the assumptions one makes about UG should have empirical content, i.e. they should be falsifiable. The approach in terms of principles and parameters is more flexible, having higher explanatory power; the modularity of grammar reflects a more general presupposition regarding the modularity of mind.