This special issue of Nordic Journal of Linguistics is dedicated to diachronic generative syntax in the North Germanic languages. With the introduction of generative grammar in the late 1950s the historical perspective became less prominent within linguistics. Instead, contemporary language, normally represented by the researcher’s own intuitions, became the unmarked empirical basis within the generative field, although there were some early pioneering studies in generative historical syntax (e.g. Traugott Reference Traugott1972). It was not until the introduction of the Principles and Parameters theory in the 1990s that diachronic syntax emerged as an important domain of inquiry for generative linguists. Since then, the study of syntactic change has added a temporal dimension to the overall enterprise to better understand the nature of variation in human language.

The syntax of the North Germanic languages proved to be a particularly promising empirical field. The linguistic diversity is conveniently limited geographically and it can be traced through time in texts from all over the Nordic countries. The pioneering investigators of syntactic variation and change in North Germanic took an interest in a variety of phenomena, including the internal order between verbs and objects, null subjects and subordinate clause word order. However, since the theoretical framework of the time was not designed to handle all the subtleties of language variation, the differences between the North Germanic varieties often appeared to be more clear-cut than they proved to be on further study. By contrast, today, a core approach within syntactic research is micro-variation. It sheds new light on previously researched phenomena and uncovers other phenomena. Consequently, it should be fruitful to revisit many of the issues raised in the past, adding the micro-comparative perspective of contemporary linguistic theory.

Within the Principles and Parameters theory, the correlation between syntactic variation and change and morphological developments has been intensively debated over the years. To begin with, many scholars assumed a direct link between morphology and syntax (see e.g. Falk Reference Falk1993, Rohrbacher Reference Rohrbacher1994, Holmberg & Platzack Reference Holmberg and Platzack1995, Vikner Reference Vikner1995). Later on, the robustness of the link was toned down (Bobaljik & Thráinsson Reference Bobaljik and Thráinsson1998, Alexiadou & Fanselow Reference Alexiadou, Fanselow, Jan-Wouter and Abraham2002, Sundquist Reference Sundquist2003), and even the correlation itself was questioned (Bentzen et al. Reference Bentzen, Hrafnbjargarson, Hróarsdóttir and Wiklund2007). Quite recently, however, the idea of an interdependence between verbal inflection and verb raising – the so-called Rich Agreement Hypothesis (RAH) – has been revitalised (Koeneman & Zeijlstra Reference Koeneman and Zeijlstra2014, Tvica Reference Tvica2017).

In addition to the theoretical developments, methodical advances, not least in computational linguistics, along with investments in linguistic infrastructure (Wallenberg et al. Reference Wallenberg, Ingason, Sigurðsson and Rögnvaldsson2011, Borin, Forsberg & Roxendal Reference Borin, Forsberg and Roxendal2012) have made it possible to perform large-scale investigations using diachronic text corpora. Hence, hypotheses about language variation and change in North Germanic languages can now be tested on much more robust empirical grounds than ever before.

This special issue of Nordic Journal of Linguistics comprises three studies on North Germanic syntax from a diachronic perspective. In her article ‘Cataphora, expletives and impersonal constructions in the history of Icelandic’, Hannah Booth discusses the emergence of the expletive það in Icelandic impersonal constructions. In Old Icelandic (1150–1350), cataphoric það could co-occur with a clausal argument and, according to Booth, behaved positionally as a subject in contexts with clausal subjects, whereas it represented the function of an initial topic place holder in contexts with clausal objects. Building on corpus data, Booth argues that það has spread from early clausal argument contexts to impersonal constructions without clausal arguments. This change takes place at the same time as cataphoric það is increasingly restricted to topic position in contexts with clausal subjects. Booth interprets this change as a development from það as a cataphoric subject to a prefinite topic position place holder. In constructions without clausal arguments, það first occurred in prefinite contexts with predicates which mean ‘say’. According to Booth, say-type predicates are a distinctive feature in contexts where prefinite það is well attested in Old Icelandic, i.e. with clausal arguments. It should, however, be noted that það in some of these early examples is ambiguous between a referential and a non-referential interpretation, and hence provides a bridge context for the later development of það into a topic position place holder. Booth bases her investigation on corpus data from the Icelandic Parsed Historical Corpus (IcePaHC; Wallenberg et al. Reference Wallenberg, Ingason, Sigurðsson and Rögnvaldsson2011). IcePaHC consists of about 1 million words from 61 text extracts covering all attested stages of Icelandic (1150–2008).

Data from IcePaHC are also used by Alexander Pfaff in his article ‘Reunited after 1000 years: The development of definite articles in Icelandic’. The topic of Pfaff’s study is definite noun phrases modified by adjectives in Icelandic. Pfaff distinguishes seven patterns of definite noun phrases modified by adjectives. He shows that the standard pattern of adjectival modification in Modern Icelandic (e.g. guli hesturinn ‘the yellow horse’) was only very rarely attested before the 17th century, whereas a double definiteness pattern, hinn guli hesturinn, otherwise associated with Swedish and Norwegian, disappeared as late as in the early 20th century. Moreover, modification with sá – sá guli hestur(inn) ‘the yellow horse’ – was dominant between the 16th and the 19th century. Pfaff points to the fact that this competition between two adjectival articles resembles an earlier situation in Mainland Scandinavian. According to Pfaff, the Proto Norse demonstrative hinn has been transformed into an adjectival article during the Viking Age. In its reduced form, inn has later cliticized to a preceding noun, forming a prosodic phase together with the noun. Pfaff argues that the result of this reanalysis is that there are two distinct article elements by the beginning of the Old Icelandic period: on the one hand the freestanding article that is part of the adjective phrase, and on the other hand a suffixal form that occupies a low head position in the nominal projection. As far as Modern Icelandic is concerned, Pfaff adopts the idea that both the freestanding and the suffixed article elements are two different surface expressions of the same underlying element that occupies a high position in the nominal projection.

In the third article of the collection, ‘The Rich Agreement Hypothesis and varieties of embedded V2’, Hans-Martin Gärtner contributes to the recent debate on the validity of the RAH. The hypothesis stipulates that finite verbs (Vs) that are richly inflected have to move from the V-domain, across sentence adverbials (Adv), into the I-domain, creating V–Adv word order. A verb has rich inflection if it agrees with the subject in both person (first, second or third) and number (singular or plural). Verbs that do not live up to this level of richness are assumed to always remain in VP, which leads to Adv–V order. In their defense of the RAH, Koeneman & Zeijlstra (Reference Koeneman and Zeijlstra2014) dismiss apparent counter-examples from Early Modern Danish, lacking verbal agreement but still displaying V–Adv word order in subordinate contexts, on the ground that they represent embedded CPs; in such cases, all verbs precede Adv because they move to C. However, Heycock & Sundquist (Reference Heycock and Sundquist2017) claim that Koeneman & Zeijlstra’s (Reference Koeneman and Zeijlstra2014) CP analysis is unjustified, since embedded V2 should be restricted to assertion-friendly contexts, typically that-clauses, while the examples at hand include a wider variety of subordinate clauses. This is where Gärtner enters the scene, calling for methodological caution. To be able to determine whether embedded V–Adv order reflects V-to-C or V-to-I movement, he argues, one needs to begin by sorting out how liberal the variety in question is when it comes to embedding CPs. In fact, there are North Germanic varieties (in the present and the past) where the use of embedded CPs goes beyond the assertion-friendly that-clauses. According to Gärtner, the status of Early Modern Danish in this respect is, at present, unclear. Consequently further corpus studies are called for, in Early Modern Danish as well as in other North Germanic varieties.

From their different areas of enquiry, the articles in this special issue illustrate how a diachronic perspective can shed new light on issues in theoretical linguistics. Hence, they contribute not only to the theoretical development but also to our understanding of human language in a broader perspective.