In September 1901, a newly elected government announced in Amsterdam its will to quickly devise and put into practice an 'ethical colonial policy’ (etische koloniale politiek) whose aims were the “moral advancement” and improvement of the “€œmaterial well-being” of the East Indian natives (ancestor of Indonesia). This reformist project was actually much older than the only electoral chronology show it to be. Its main themes were already articulated in the late 1840s in the exchange of fire between the Liberals and the Conservative Party, and then again in the spectrum of puritan conservatism and social democracy in the politics of the Netherlands in the 1870s. From 1901 to 1926, this so-called Ethicist movement inspired new discussions but mostly new administrative practices in the Insulinde Dutch East Indies. The movement was backed just by a handful of resourceful individuals belonging to the closely connected worlds of Law, Sciences and Politics. Coming from very different ideological backgrounds and harboring distinct political aims, the Ethicists were a key component of Europe-wide networks of colonialist societies - and this gave them the strength they needed to fight with their enemies inside the colonial bureaucracies. Because of the repressive turn of 1926 however - when the crushing of the communist revolts in Java and Sumatra led to the sudden conservative radicalization of the colonial government -, the Ethicist program was definitively shelved. Only a handful of high profile officials, gathered in the Stuw Group, held up the program in the 1930s - most of whom later took an active part in post-WWII bloody anti-nationalist policies. The purpose of this article is to put under scrutiny the careers of some of the main proponents of this 'moral reform’ of the Dutch colonial project.