The origin and early use of periphrastic do has intrigued scholars for a considerable period of time, and it has been described as one of the great riddles of English linguistics. An early study of the topic, Ellegård 1953, found a peak in the use of do in affirmative declarative clauses in the second half of the 16th century, more specifically between 1550 and 1575, while some recent studies (eg Rissanen 1991, Bækken 1999, Wischer 2000) suggest that this peak may have occurred somewhat later. The present paper addresses the use of do in affirmative declarative clauses in 17th century English. The investigation is based on occurrences of do in a corpus consisting of declarative main clauses beginning with a non-subject constituent. The examples derive from different text types, and the material will be investigated with a view to trying to ascertain to what extent the use of do differs between the various texts and text types. The examples will be further discussed from the point of view of morphological, syntactic, semantic and pragmatic factors that may have favoured the use of do, and comparisons will be drawn with other studies of do in the period in question.

References
Bækken, Bjørg. 1999. "Periphrastic do in Early Modern English". Folia Linguistica Historica XX/1-2: 107-128.
Ellegård, Alvar. 1953. The auxiliary do. (=Gothenburg Studies in English II) Stockholm: Almqvist & Wiksell.
Rissanen, Matti. 1991. "Spoken language and the history of do-periphrasis". In Dieter Kastovsky ed. Historical English Syntax. (=Topics in English Linguistics 2): 321-342. Berlin and New York: Mouton de Gruyter.
Wischer, Ilse. 2000. "What makes a syntactic change stop? On the Decline of periphrastic DO in EModE affirmative declarative sentences". Paper read at the 11ICEHL, Santiago de Compostela.