The letters signed Cassius were, at the time of publication, generally accredited to the pen of James Sullivan, and this opinion is adopted in Amory's Life of James Sullivan. The letters themselves bear out this opinion, being clearly written by a partisan of the Hancock faction, of whom Sullivan was a warm adherent, and constant newspaper essayist.

The first two letters were printed before the promulgation of the proposed Constitution in Massachusetts, and chiefly relate to the differences between the two parties headed by John Hancock and James Bowdoin; but are included here to complete the series. The letters are of particular value as giving the position of Hancock, of whom Sullivan was the particular mouthpiece, proving him to be a supporter of the adoption of the Constitution, though the contrary has often been asserted. The early letters were commented upon by “Old Fog,” in the Massachusetts Centinel of Sept. 22 and Oct. 6, 1787.