Differences between real and colourable motives--War atrocious without either of these motives--Wars of plunder, under the most plausible pretexts, not justifiable--Causes apparently, but not really just--Unnecessary advantage--Desire of a better soil--Discovery of things belonging to others--Incapacity of the original owners--War not always justifiable under the pretext of asserting liberty--Or of imposing a beneficial government upon a people against their will--Emperor's pretensions to universal empire refuted--Pretensions of the Church--Imperfect obligations--Difference between wars originally unjust and those afterwards becoming so. I. In a former part of this work, where the justice of war was discussed, it was observed that some wars were founded upon real motives and others only upon colourable pretexts. This distinction was first noticed by Polybius, who calls the pretexts, προφασεις {prophaseis}, and the real causes, αἰτιας {aitias}. Thus Alexander made war upon Darius, under the pretence of avenging the former wrongs done by the Persians to the Greeks. But the real motive of that bold and enterprising hero, was the easy acquisition of wealth and dominion, which the expeditions of Xenophon and Agesilaus had opened to his view. In the same manner, a dispute about Saguntum furnished the Carthaginians with COLOURABLE MOTIVES for the second Punic war, but, in REALITY, they could not brook the indignity of having consented to a treaty, which the Romans had extorted from them at an unfavourable moment; and more especially as their spirits were revived by their recent successes in Spain. The real causes assigned by Thucydides for the Peloponnesian war, were the jealousies entertained by the Lacedaemonians of the then growing power of the Athenians, though the quarrels of the Corcyreans, Potidaens, and other secondary states were made the ostensible reasons. II. There are some who have neither ostensible reasons, nor just causes to plead for their hostilities, in which, as Tacitus says, they engage from the pure love of enterprise and danger. A disposition to which Aristotle gives the name of ferocity. And in the last book of his Nicomachean Ethics, he calls it a bloody cruelty to convert friends into enemies, whom you may slaughter.