A Discourse Concerning Puritans and The Case of Shipmony were Henry Parker's first two pamphlets of the Long Parliament era. Their place order in the Thomason collection shows them to be amongst the first tracts Thomason collected; Thomason probably acquired, or at least annotated, them at about the same time, most likely early in 1641. Though the two pamphlets overlap, notably in their appreciations of the role and the enemies of the parliament, they also inaugurate two separate lines of Parker's reflection, one more or less “divine” and the other unabashedly “politic.” The Case of Shipmony is the headwater of the political stream. As such it occupies a special place in the history of English political thought: The Case of Shipmony may be the first intellectually significant printed political pamphlet of the Long Parliament era. For a long time, there was nothing quite like it, apart from Calybute Downing's several efforts and a private person's reply to a parliamentary speech that may well be by Parker.

The pure, freestanding printed political tract (so familiar in mid–1642 and after) was not a natural mode of expression in 1640–1. Of course, this is not to deny that political reflection of a fairly high order went on in England in the 1620s and 1630s. But it did not take this form. Printed publication was apparently a critical, and initially inhibiting, factor.