Observations opened the flood gates to a new kind of political reflection. The royalist counterattack and even the less than enthusiastic response that Observations received in some parliamentary circles raised a question: would Observations be swept away by torrents of its own making? Twice Parker gave in to the urge to answer his critics, first in an occasional pamphlet, The Contra-Replicant, which Parker used as a vehicle for the expression of a far broader set of concerns (which he further developed in The Oath of Pacification), and later in Jus Populi, Parker's most extended excursion into speculative political thought.

The Contra-Replicant was a pièce de cirConstance. At a time when Parker's behind-the-scenes activities at the Committee of Safety would have been easily more than one man's labor, a well-conceived and quite massive royalist “peace” campaign to stir up trouble in London drew Parker back into the public fray. As Parker later remembered the situation, “About the beginning of 1643 [actually December 1642–January 1643] another black desperate designe against the City of London was discovered, scarce inferiour to any of those former impregnations of the Kings inraged brain.” The urgency of the mission was not only political. The peace campaign's slogans pierced Parker'sown flesh; in reaction The Contra-Replicant allowed itself an unusually long tether, and proved to be amongst the most impassioned and self-revelatory of Parker's writings.