But almost all the other lines afford many examples of men who killed their sons, and of many who killed their mothers and wives; and as for men killing their brothers, just as geometricians assume their postulates, so this crime came to be a common and recognized postulate in the plans of princes to secure their own safety.
Edition :
Plutarch. Plutarch's Lives. with an English Translation by. Bernadotte Perrin. Cambridge, MA. Harvard University Press. London. William Heinemann Ltd. 1920. 9.