On 25 September 1660, the States of Holland under the prime movers of De Witt, Cornelis de Graeff, his younger brother Andries de Graeff and Gillis Valckenier resolved to take charge of William's education to ensure he would acquire the skills to serve in a future—though undetermined—state function. Influenced by the values of the Roman republic, De Witt did his utmost anyway to prevent any member of the House of Orange from gaining power, convincing many provinces to abolish the stadtholderate entirely. He bolstered his policy by publicly endorsing the theory of republicanism. He is supposed to have contributed personally to the "Interest of Holland", a radical republican textbook published in 1662, by his supporter Pieter de la Court.