An usefull case of conscience discussed and resolved : concerning associations and confederacies with idolaters, infidels, hereticks, or any other known enemies of truth and godlinesse. By Master George Gillespie, late minister at Edinburgh. Whereunto is subjoyned a letter, written by him to the commissioners of the Generall Assembly, in the time of his sicknesse: together with his testimony unto this truth, written two dayes before his death.