In his five decades of research, he practiced a Franciscan philosophy of knowledge in action. He was not content to speculate about these new peoples, but met with, interviewed and interpreted them and their worldview as an expression of his faith. While others – in Europe and New Spain – were debating whether or not the indigenous peoples were human and had souls, Sahagún was interviewing them, seeking to understand who they were, how they loved each other, what they believed, and how they made sense of the world. He fell in love with their culture. Even as he expressed disgust at their continuing practice of human sacrifice and their idolatries, he spent five decades investigating Aztec culture.