Aerssens owed much to the Advocate, but he attributed his removal from his post at the French court to the decision of Oldenbarneveldt to replace him by his son-in-law, Van der Myle.

He never forgave his recall, and alike by subtle insinuation and unscrupulous accusation, strove to blacken the character and reputation of his former benefactor.
By a curious fatality it was the outbreak of fierce sectarian strife and dissension between the extreme and the moderate Calvinists which was eventually to change the latent hostility of Maurice to Oldenbarneveldt into open antagonism.

Neither of the two men had strong religious convictions, but circumstances brought it about that they were to range themselves irrevocably on opposite sides in a quarrel between fanatical theologians on the subject of predestination and grace.
From early times Calvinism in the northern Netherlands had been divided into two schools.

The strict Calvinists or "Reformed," known by their opponents as "Precisians," and the liberal Calvinists, "the Evangelicals," otherwise "the Libertines." To this Libertine party belonged William the Silent, Oldenbarneveldt and the majority of the burgher-regents of Holland.

These men regarded the religious question from the statesman's point of view.