The Syntax of Let Construction in English: A Systemic Functional Approach

The syntactic issue of English let construction has long been one of the hot topics in linguistic research. Opinions about its syntax are various among grammarians, especially about the problem of how to deal with let. Systemic functional grammar claims that the relationship between meaning and form is realization, e.g. meaning is realized in form. Meaning is the generative base of systemic functional grammar. Therefore, the principle of functional syntactic analysis is that functional syntactic analysis should be “meaning-centered.” Based on the basic principle of functional syntax and COCA (Corpus of Contemporary American English) data, the paper aims to investigate the syntax of let construction within systemic functional approach. It is concluded that English let construction has two different functional structures: one is canonical imperative let construction; the other is specialized imperative let construction. As for the functional syntax, let within the canonical imperative let construction should be analyzed as the Main Verb, and let within the specialized imperative let construction should be analyzed as the direct element of the clause, that is Let element. Functional syntactic analysis has its own principles, features, and methods. The academic explorations based on systemic functional theory are of great significance both theoretically and practically.


Introduction
Systemic Functional Grammar (SFG), which is under the guidance of anthropology and sociology, takes meaning as the point of departure for linguistic investigation. For SFG, language is a multi-level system involving context, semantics, lexicogrammar and phonology (orthography), and the relationship between linguistic meaning and form is that of realization. The fundamental principle in SFG is that of "meaning as choice." Based on Systemic Functional Grammar (Halliday [1]; Fawcett [2,3]), the paper aims to investigate the syntax of let construction (i.e. Let us go; Let's go for a walk; Let them beware! etc). Let construction has been investigated by traditional grammar and other grammatical theories, but in terms of its syntax, especially the problem of how to deal with let, no agreement has yet been reached.
The paper divides into four parts. The first part states the research background of the syntax of let construction and discusses the limitations of the previous research. The second part deals with the theoretical framework for the present research. In the third part, the syntactical analysis of let construction is to be conducted within the principle of systemic functional syntax. And finally a conclusion will be made.

Previous Studies on Let Construction
Modern grammatical investigation on let construction can go back to Jespersen [4]. After Jespersen, the semantics and syntax of let construction has been a constant concern among grammarians and linguists (Seppänen [5]; Quirk et al [6]; Davies [7]; Clark [8]; Potsdam [9]; Biber et al [10]; Huddleston & Pullum [11]; Alcazar & Saltarelli [12]; Halliday [1]). Since the purpose of this paper is to investigate the syntax of the construction from SFG perspective, the paper shall only review some representative viewpoints on the syntax of the construction, and no comment on these studies any further.
Quirk at al divide imperatives into three categories: first person imperative, second person imperative and third person imperative [6]. let construction falls into first person imperative (e.g. Let me open the door; Let's open the door) and third person imperative (e.g. Let someone open the door). Syntactically they regard let in first and third person imperatives as an auxiliary, the nominal phrase after let as a subject in the objective case, the verb after the nominal phrase as the Main Verb. As for let's construction, they treat it as an unanalyzed whole, which could be regarded as a particle. As for their analysis, despite their insights, two limitations are obvious to see. One is that let does not have the grammatical features that an auxiliary verb owns. The other is that it is not clear which syntactic element should let's fill in.
Huddleston and Pullum [11] classify imperatives into ordinary imperatives (e.g. Please let us borrow your car) and let-imperatives. Let-imperatives are marked by a special use of let distinct from the normal use with the sense "allow". Let in the "allow" sense is found in all clause types, but in let-imperative, let has been bleached of this meaning and serves as a marker of this special type of imperative construction. They further classify let-imperatives into 1 st person inclusive let-imperatives (e.g. Let's open the window) and open let-imperatives (e.g. Let that be a lesson to you; Let me receive the credit; Let him say so etc.). Semantically they indicate that let in let-imperatives has lost its propositional meaning. It does not contribute to the propositional content, does not help specify what action would constitute compliance with the directive. It serves, rather, as a marker of illocutionary meaning. But syntactically they think there is no compelling reason to suggest that there has been a reanalysis of the syntactic structure and no positive grammatical property that sets let-imperative clauses apart as a distinct construction. They group let-imperatives grammatically with ordinary imperatives, treating the difference as a matter of meaning and use rather than form. Therefore syntactically they analyze let-imperatives as containing the catenative verb let together with an NP object and (except in ellipsis) a bare infinitival clause as second complement. This kind of syntactic analysis attempts to unify let construction and ordinary imperative syntactically in the same model. The drawback of the analysis is that it is only based on form rather than meaning, which ignores the relationship of realization between form and meaning.
Alcazar and Saltarelli [12] combine Performative hypothesis (Ross [13]) and "light" verb hypothesis (Chomsky [14]) and propose the "light" performative hypothesis (LPH). They subcategorize imperatives into canonical imperatives (e.g. go!) and hortatives (let…go!). The LPH proposes that the imperative clause is uniquely characterized by the presence of a functional "light" v. This auxiliary-like verb defines the imperative type as a "prescription". In canonical imperatives, the speaker prescribes that the addressee carry out a (virtual) action or activity. In hortatives, the speaker prescribes that the addressee cause (or 'see to it that') somebody to carry out the prescription. They argue that hortatives are causative or proxy imperatives prescribed through the mediation of a light causative c, the various choices in imperative-hortative meaning determined by the strength of the prescription. In their theory, syntactically they recognize three subject arguments in hortatives, namely the Speaker or "logical" subject, the Addressee or "grammatical" subject of prescription, and the Performer or "actual executor." Though with great insights in their analysis, their analysis is also based on form rather than meaning. From the functional and grammaticalizational perspective, whether let in most of the hortatives still has causative sense in modern English is disputable. And it is arguable whether the Addressee is always the causer of the action in hortatives (e.g. let's construction).
In Systemic Functional Grammar, Halliday [1] mostly adopts the classification of traditional grammar and classifies imperatives into first, second and third person imperatives. He proposes that imperative is the mood for exchanging goods-&-services, and its Subject is 'you' or 'me' or 'you and me'. Based on the paradigm and speech function, he argues that let's is best interpreted as a wayward form of the Subject 'you and I'. He claims the only anomalous form then is the response Yes, let's!, No, let's not!, which on the analysis has Subject and no Finite. Halliday also argues that let me construction (e.g. Let me go!) may be interpreted as imperative on the analogy of let's. However, the meaning of 'offer' is dependent only on the particular goods-&-services referred to: if the meaning required is 'allow me to', the same form will be heard as a command with let as second person imperative. Hence an expression such as let me go is ambiguous: either offer, first person imperative (= 'I offer to go', with the tag shall I?), or command, second person imperative (= 'release me', with the tag won't you? or will you?). He argues that if Subject required is a pronoun in third person imperative, it will always be accompanied by let as in let them beware! Halliday's analysis is of great insight from the functional perspective, but syntactically his treatment of let-imperative such as, let me/him/them construction is not very clear, especially the problem of let in the construction.
Based on the semantic functions of let construction, Fawcett [2,3] argues that let in traditional first person and third person imperatives has been grammaticalized into an imperative marker. He analyzes let in let imperatives as the direct element of the clause (that is Let element), the nominal group following let as the Subject, and the verb after the nominal group as the Main Verb. For example: Fawcett's analysis is based on the functions of let in the let construction, which is guided by the "meaning as choice" principle of SFG, but his analysis of let is solely focused on hortatives [12] or let-imperatives [11] and ignores the analysis of let construction in ordinary imperatives.
Besides the above scholars, others have also conducted some relevant researches into the syntactic issues of let construction (Seppänen [5]; Davies [7]; Clark [8]; Potsdam [9]; Xu [15]; Biber et al [10]; He [16]; Morley [17]), and come out with some deep insights. However, like the scholars stated above, most of the syntactic analyses are based on form, and lack the systematic explorations of the meaning of let construction. This paper agrees with Fawcett's view, but as stated above, his analysis is not systematical, which ignores other let constructions, such as, let me/us/there constructions. The sections next below will first introduce some basic syntactic principles of SFG, and then under the guidance of the principles to analyze the syntax of let construction from the perspective of SFG.

Theoretical Framework for the Analysis of Let Construction
The theory of SFL is developed from a theory of syntax, and syntax is of great significance to SFL. The theory of SFG is marked by Halliday's Categories of the theory of grammar [18]. After decades of development and revision, different models have been formed, among which Fawcett's [2,3] syntactic theory has been very influential. This section mainly focuses on Fawcett's "Cardiff grammar" model of SFG.

Form and Meaning
Saussure's most basic concept was that of the "linguistic sign". For Saussure, any "sign" consists of a "signifier" and a "signified", i.e. a form and a meaning. Fawcett [19] adopted Saussure's view on linguistic signs. He claims that human linguistic signs include two levels: form and meaning. For Fawcett, meaning and form are two aspects of the linguistic signs. We cannot expect to understand the forms of language without considering the meaning of language, and vice versa. Meaning and form in language are mutually defining. Paradigmatic relation is a contrast between meaning rather than form. In his model of SFG, the primary concern is meaning that matters, not the forms. Forms are the structural realizations of meaning. Language as the resources of making meaning for human communication, its output is a text. The distinction between a language and a text can be expressed in more general terms as the distinction between a potential and an instance. So, Fawcett's model of language has the two levels of meaning and form, as can be seen from Figure 1 below. (Fawcett [3]).

Figure 1. The components and their outputs in a systemic functional grammar
As we can see, the pair of boxes on the left represent the components of any semiotic system, and the pair on the right the outputs from those components. In Fawcett's model, lexicogrammar has two main components that specify 'potentials' (on the left), and two outputs that specify 'instances' (on the right). Thus the system network of semantic features specifies the language's meaning potential, and the realization rules specify its form potential, their output being a syntactic unit and its elements. As Figure 1 shows, the selection expression of features chosen on a traversal of the network becomes the input to the realization rules. If an element of the generated unit needs to be filled by a further unit, a realization rule (represented by the arrow on the left) specifies re-entry to the network to generate one.

Basic Categories and Relations of Syntax
In the "Cardiff grammar" version of SFG, the minimal theory of syntax includes eight simple concepts, which can be divided into four basic categories and four basic relationships. The four categories are Unit, Place, Element and Item. And the four basic relationships are Componence, Filling, Exponence, and Conflation. The four basic categories and four basic relationships can be represented in Figure 2 below. In Figure 2, at the top of the tree diagram is the unit of the clause, and it has, in this instance, five elements, that is, S, O, M, C, and A. The third category in Figure 2 is the item. The item is usually is a word, but sometimes an item may consist of more than one written word. The place is the row numbered in a unit at which the elements are located. The four relationships, as is seen on the right part, can be summarized in the following statement: (i) a unit is composed of one or more element; (ii) some elements are directly expounded by items; (iii) other elements are filled by a unit; (iv) any such unit is itself composed of one or more element; (v) the lowest element is expounded by an item; (vi) some elements are conflated with some other elements.
As for the instance in the Figure, the unit clause is composed of five elements, the Subject element is filled by a nominal group, which is composed of head only and expounded by the item Ivy. The element Operator is conflated with Auxiliary and together directly expounded by will. The element Main Verb is also directly expounded by wash. The Complement element, which is filled by a nominal group, is composed of a deictic determiner and a head, and expounded by her and hair. The last element Adjunct is filled by a nominal group, which again composed of two elements, and expounded by this and evening.
Cardiff Grammar is consistent with the basic idea of SFG, and takes its departure in investigating language system from meaning. Its basic methodology is starting from "above". Therefore, in terms of linguistic description, more emphasis is put on the principle "centering on meaning, form being the realization of meaning". As for the relationship between meaning and form, the system network models choice between semantic features, i.e. meaning. And meanings are the generative base of a SFG. The result is that the purely formal contrasts in a language play no role in how the grammar operates in the generation of a sentence. In Cardiff Grammar version of SFG, syntax has been greatly emphasized in linguistic research. Meaning and form are bidirectional.

Systemic Functional Syntactic Analysis of Let Construction
Halliday [20] points out that "Systemic, or systemic-functional theory is functional and semantic rather than formal and syntactic in orientation, takes the text rather than the sentence as its objects, and defines scope by reference to usage rather than grammaticality." And Fawcett [3] also states that "Meanings are the generative base of a systemic functional grammar." So, the aim of functional syntactic analysis is to study how meanings are realized by form. Form analysis serves for meaning analysis, and syntactic analysis cannot be departed from semantic analysis.

The Semantic Evolution of Let
As Halliday [21] claims "the internal organization of language is not arbitrary but embodies a positive reflection of the functions that language has evolved to serve in the life of social man". Language is constantly evolving to serve for social functions. Grammaticalization as one the important ways of language evolution is the process whereby lexical items and constructions come in certain linguistic contexts to serve grammatical functions, and once grammaticalized, continue to develop new grammatical functions [22]. Basic to work on grammaticalization is the concept of a "cline". From the point of view of change, forms do not shift abruptly from one category to another, but go through a series of gradual transitions. The term "cline" itself has both historical and synchronic implications. From a historical perspective, a cline is a natural pathway along which forms evolve, a kind of linguistic "slippery slope" which guides the development of form. Synchronically a cline can be thought of as a "continuum": an arrangement of forms along an imaginary line at one end of which is a fuller form of some kind, perhaps "lexical," and at the opposite end a compacted and reduced form [22]. So, from the grammaticalizational process, meaning may persist in the evolved linguistic forms, and the process of grammaticalization may undergo the process of "A>A/B>B", which makes language become more ambiguous and metastable.
The meaning of the English verb let has experienced the grammaticalizational process. Its original meaning of "allow" has been becoming more and more unspecific, and has become the mood marker centered on speaker's attitude. However, because of the semantic "persistent" principle of grammaticalization, the meaning of let in modern English has the characteristics of metastableness. The content meaning fuses with grammaticalized meaning. The result is that the same linguistic form comes out with different meanings, and forms different imperative constructions. From the view of evolution of let, the paper agrees with Huddleston & Pullum's classification of let construction. The paper divides let construction into two broad categories: ordinary imperative let construction and specialized imperative let construction, and the latter can be further divided into let's construction and open let imperative construction.

Syntactic Analysis of Ordinary Imperative Let Construction
As ordinary imperative, this type of let construction has the basic grammatical features of ordinary imperatives. The subject of this type of let construction is optional, and its verb has the base form: (2) a. Please let us borrow your car. [11] b. Dammit, Bob, you let me go! (COCA 1992) c. "Don't let him go down," she shouts. (COCA 2015) Semantically, clauses a, b and c in example (2) can be roughly paraphrasable with: "You please allow us to borrow your car"; "You should allow me to go"; "You should not allow him to go down". Let in this type of construction keeps the meaning of "allow". The whole construction expresses not the sense of "you should allow or not allow somebody", but "you should allow or not allow somebody to do something".
Thus from semantic point of view, the nominal group following let (i.e. us, me, him in the above examples) is semantically closer to the verb following the nominal group (i.e. borrow, go, go), which form a complete event. The item let with "allow" sense in the above examples is only related with the following event, which expresses a certain degree of "influence". Based on the principle of "A participant role is a role that is 'expected' by the process [3]", this type of let construction has the "causer", that is, an Agent, no matter it is overt or covert. Mostly the "causer" is the addressee.
Therefore, according to Cardiff Grammar, this type of let construction can be, in transitivity terms, analyzed as influential process. The process has an Agent to "influence" an embedded event, that is, Phenomenon. So to treat let in this type of construction as a light verb [12] or catenative verb [11] ignores the meaning of let, and to analyze the nominal group following let as the Object ( [6,11]) ignores the semantic relations between the nominal group and its following verb. The result of the analyses is based on form rather than meaning, which cannot reveal the semantics of this type of let construction.
Based on its semantic functions and relations of this kind of let construction, the paper, syntactically, analyzes let as a Main Verb, the Agent of the process of let (i.e. the addressee) as Subject, which can be covert and overt (if covert, it will be represented in round bracket), and the embedded clause following let as the Complement, which can be further analyzed. The syntactic analysis of example (2) is suggested in Figure 3:

Syntactic Analysis of Specialized Imperative Let Construction
As stated above, this type of let construction can be further classified into let's construction and open let imperative construction. This section will analyze its syntax separately with two subsections. The first subsection analyzes let's construction, and the next subsection analyzes open let imperative construction.

Syntactic Analysis of Let's Construction
As stated in Section 2 above, grammarians differ in the  (3) is both the speaker and the addressee. Each clause in example (3) just has one process, which is realized separately by be, enjoy, count, forget, ask, get out of. Let in this construction is paraphrasable with deontic should, which is greatly grammaticalized. So example (3a), (3b) and (3c) are roughly equal to "We should be honest", "We all should enjoy it", and "Do we should count." From the perspective of paradigmatic features in example (3), the syntactic analysis must capture all the paradigmatic features, such as, the Operator for do in the 'pressing' version of this construction (i.e. where the Speaker is 'pressing' the Addressee to take part in the proposed action), the Operator for don't in the typical 'negative' polarity version, the words both and all for 'quantifying' the referent of the word us (whether us is expressed in full or in the contracted form of 's). So, to treat let's as an unanalyzed whole ( [6]) or to analyze let's as Mood Adjunct ( [15,16,17]) can only explain example (3f), because let's in this clause has been completely grammaticalized, which only serves as an imperative marker. However, treating let's as Mood Adjunct cannot capture all the other paradigmatic features in example (3). This kind of analysis ignores the origin of let's (i.e. let us), and makes the Subject of the let's construction without structural dependence, which cannot capture the 'pressing' function of do, the 'quantifying' function of both and all. Halliday's [1] treatment of let's as a wayward form of Subject besides cannot capture the usage of example (3f), the most important drawback is that there are no grammatical commonplace between this kind of Subject and other Subject, which is wayward indeed.
Based on the semantics and paradigmatic features of let's construction, the paper tends to agree with Fawcett's [2,3] analysis. Let in this kind of construction has been greatly grammaticalized, but it has no similarities with other auxiliaries (which can often be conflated with Operator). Following Fawcett, since there is no item other than let that expounds this element, this paper analyzes let in this construction as the direct element of the clause, that is, let element (abbreviated as L element). This kind of analysis can capture all the paradigmatic features in let's construction. Therefore, syntactically the paper treats 's as the contracted form of us, and analyzes it as the Subject, the verb after let's as the Main Verb. As for example (3f), because let's in this clause has been grammaticalized so much deeper and only functions as an imperative marker, the paper analyzes let's in this clause as Let element. The syntactic analysis of example (3) is shown in Figure 4 below:

Syntactic Analysis of Open Let Imperative
Construction Open let imperative construction mainly refers to the third person imperative construction in traditional grammar [6], yet just as Huddleston and Pullum point out, "in principle the full range of person-number combinations is permitted" [11]. The paradigmatic features of this kind of let construction are as follows: (4) a. Let that be a lesson to you. ( This kind of open let imperative construction is not understood as directives to the addressee(s) to allow or permit something. This type of let construction can be used where the speaker has no specific addressee(s) in mind. They are therefore somewhat peripheral members of the speech act category of directives [11]. So open let imperative construction is not likely to insert you as Subject, or to have an interrogative tag such as will you? And as with let's construction, there is no semantic scope contrast with negatives. Let …not is a great deal more likely than don't let. So, semantically clauses of this type of let construction are not real directives, but rather with mood meanings like "deontic", "wishing", "supposing", and so on. Example (4a), (4b) and (4d) in example (4) above are paraphrasable with "That should be a lesson to you", "He should say so", and "We all should work hard"; whereas example (4e) and (4h) are paraphrasable with "Suppose LINEi equal the total number of line items", and "I wish there be light". Therefore, to treat let in this type of construction indiscriminately as light verb [12] or catenative verb [11] cannot capture its semantic functions, and to treat let as an auxiliary [6] captures its semantic function, but it is still disputable as for the universalities between this type of auxiliary and other common auxiliaries.
From the perspective of semantic force of imperatives, open let imperative construction is peripheral, and let has been further grammaticalized, which only serves as the imperative marker. So, according to the semantic functions of let in this type of construction, the paper also analyzes let in this kind of construction as Let element, the nominal group following let as the Subject, and the verb following the nominal group as the Main Verb. The analysis of example (4) is suggested in Figure  5 below:

Conclusion
Linguistic research can take meaning as well as form as its starting point. This paper, based on the syntactic theory of SFG, takes its departure from the relationship of realization between meaning and form, and analyzes the syntax of let construction within the basic principles of functional syntax.
It is found that let construction actually has two functional structures: ordinary imperative let construction and specialized imperative let construction, and the latter can be further divided into let's construction and open let imperative construction. Syntactically, in the ordinary imperative let construction, let is analyzed as the Main Verb; its Subject is often covert; and the embedded clause following let fills the Complement of the matrix clause. In let's construction, let is analyzed as the direct element of the clause, i.e. Let element; 's (the abbreviated form of us) is analyzed as the Subject; and the verb following let's is treated as the Main Verb. In the open let imperative construction, let is also treated as Let element; the nominal group following let is analyzed as the Subject; and the verb following the nominal group is analyzed as the Main Verb.
The syntactic analysis of let construction in this paper obeys the basic principle of SFG, i.e. "centering on meaning rather than form". Though it confines in let construction in English proper, its principles and methods involving syntactic analysis is of great enlightenment on other constructions in English and other languages. Functional syntactic analysis has its own principles, features, and methods. The academic explorations based on systemic functional theory are of great significance both theoretically and practically.