Hanke's writings documented Las Casas' work as a political activist, historian, political theorist, and anthropologist.
His scholarship also uncovered evidence to support Hanke's claim that Las Casas did not act as the sole voice of conscience during the colonial era, but actually constituted the head of what was a larger reform movement by a number of Spanish colonists to prevent "the destruction of the Indies.” His historiography was similar to the one of his contemporary Jaime Eyzaguirre.