A historical and philosophical study of Ahimsa was instrumental in the shaping of Albert Schweitzer's principle of "reverence for life". Schweitzer praised Indian philosophical and religious traditions for the ethics of "Ahimsa": "the laying down of the commandment not to kill and not to damage is one of the greatest events in the spiritual history of humankind", but suggested that "not-killing and not-harming" is not always practically possible as in self-defence, nor ethical as in chronic starving during a famine case.