A synthetic approach to long-lasting theoretical debates and the necessary condition for implementing it are discussed with concrete examples, including the very theory of the UG–iconicity interface. The popular role models of linguistics, biology and physics, are shown with certain general properties which are argued to deserve attention in linguistic research and theorization.

Categorially obscure words of relations, sometimes accompanied by semantic obscurity too, characteristically occur between the connected constituents regardless of the specific word-order setting of a language. This chapter investigates two kinds of such connectors, the conjunctions and the linkers. It is argued that the functional void of UG responsible for the grammatical behaviors of connectors is that UG cannot project any lexical item without a categorial specification. If a lexical item does not acquire a category for some independent reason, its consequential lack of syntactic representation leads to unique grammatical behavior dependent on the specific semantic relation it encodes. In the case of conjunctions, the symmetric nature of ‘and’ and ‘or’, triggering linear iconicity while restricted by the isomorphic implementation of the USM, results in representing conjuncts on parallel planes of which one is the “default” due to computational cost. It is this simultaneous symmetry–asymmetry enforced by the UG-iconicity interface that explains a large set of apparently self-contradictory traits of coordination. Linkers from Mandarin Chinese, Chamorro and Cantonese are analyzed in a similar manner.

The SVCs have a cluster of grammatical traits not derivable exclusively from UG, some of which have been misrepresented/misunderstood in the UG literature. The first functional void of UG is proposed which limits the lexicalization of a semantic relation R to only those cases where R connects first-order entities. All the characteristic properties of SVCs result from this functional void collaborating with the proposed Serial Verb Parameter (SVP) in the theory of the UG–iconicity interface. It also explains a wide range of related cross-linguistic facts, from phrasal SVCs to compounds, the parametric variations between Chinese and Gbe languages in (dis)allowing ditransitive V1, why the resultative SVC acts in a particular set of ways different from other types and the subtle disparities between head-initial and head-final SVCs, as well as the full range of variations among Kwa languages in object- and verb-fronting. The relation between the linearization pattern of UG and the iconicity-induced word order of SVCs is shown to pattern with the “high” and “low” neural pathways underlying fear, with implications on the nature of redundancy in biologically based systems and suggestive of an evolutionary connection between these two linearization mechanisms in language.

Multiple aspects of the external argument ArgE need better understanding. First, no principle of UG explains why ArgE must stay structurally outside any lexical verbal projection. This fact is argued to result from the USM requiring an isomorphic mapping between semantics and structure while UG itself cannot guarantee such a result via X'-theory. The solution is iconicity of independence, which matches ArgE’s conceptual “independent existence” (Dowty 1991) from an event with its structural separation from the projection of the event-denoting V. Second, the grammatical properties of ArgE, especially given the iconicity account, must be compared with those of oblique arguments, eventually leading to a theory of the morphology–syntax interface which allows a uniform account of several types of cross-linguistic fact. Third, regarding word order, moved constituents exhibit the earlier-iff-structurally-higher correlation while in situ constituents don’t, with ArgE typologically in both groups. This property, together with the unique word orders produced by linear iconicity in previous chapters, prompts the hypothesis that linearization results from computational cost and the 2nd law of thermodynamics, which further identifies a new locality phenomenon: the functional domain island.

This chapter deconstructs and compares two English syntactic variables as case studies to explore the linguistic/social interface in variation. The two variables are: (1) complementizer alternation (that/Ø) and (2) subject relative pronoun alternation (who/that/Ø). While both are internally and externally conditioned, the nature and strength of the predictors (also known as factors) differ significantly. I argue that the results from quantitative linguistic analysis, statistical modelling and a comparative perspective grounded in social and historical context provide unique insight into the synergy of social, cognitive, stylistic and linguistic factors. In the case of complementizers, the overwhelming influence of verb is the linguistic footprint that a particular collocation (e.g. I think) has grammaticalized into an epistemic parenthetical away from the original matrix plus complement construction. In the case of relative pronouns, the preponderance of who for subject, animate antecedents aligns with a well-known typological pattern (i.e. human animates contrast with non-humans), which is overlain with social evaluation originating from its prestigious origins that endures in current usage in the speech community. In sum, interpreting the varying roles played by multiplex influences on linguistics features is key to understanding variation.

The introduction to this volume sums up and discusses some of the issues fundamental to the study of syntactic variation, such as the problem of semantic equivalence (since syntactic variants often have different meanings), the delimitation of syntactic alternations, the relation between linguistic and social conditioning of syntactic variables, and the explanatory frameworks that are proposed in the chapters to account for the linguistic choices speakers make when employing syntactic alternants.

Sociolinguistic research demonstrates that speakers are ‘aware’ of some variables in their speech patterns, but not others, as evidenced by, for example, style shifting. In explaining this bifurcation, Labov (1993, 2008) suggests that speakers have a sociolinguistic monitor where ‘members of the speech community evaluate the surface forms of language but not more abstract structural features’. However, determining which linguistic variables are ‘surface’ and which are more ‘abstract’ is far from clear. In this chapter we test the sociolinguistic monitor by comparing the use of two variables which are considered to be abstract structural features - negative concord and use of never for didn't. We compare the use of these forms across two datasets: one where community members are in conversation with a community insider and another with a community outsider. We find that there is style shifting according to interlocutor with negative concord but not with never for didn’t, suggesting that only the former is ‘monitored’ in the speech of this community. These findings suggest that social pressures override similarities across linguistic structure in the operation of the sociolinguistic monitor.