XXXVIII. It has been shewn before, and it is a truth founded upon historical fact, that wars are undertaken, as acts of punishment, and this motive, added to that of redress for injuries, is the source, from which the duties of nations, relating to war, take their rise. But it is not every injury, that can be construed into a just ground of war. For laws, whose vengeance is meant to protect the innocent, and to fall upon the guilty, do not regard every case, as a sufficient warrant for their exertion. So that there is much truth in the opinion of Sopater, who says that there are trivial and common offences, which it is better to pass over unnoticed, than to punish. XXXIX. The maxim laid down by Cato, in his speech in defence of the Rhodians, that it is not right any one should be punished upon the bare suspicion of his having intended to commit aggression or injury, was well applied in that place; because no positive decree of the people of Rhodes could be alleged against them, nor was there any other proof beyond the CONJECTURE of their wavering in their policy. But this maxim is not universally true. For where intention has proceeded to any outward and visible signs of insatiable ambition and injustice, it is deemed a proper object of jealousy, and even of punishment. Upon this principle, the Romans, as may be seen from Livy's account in the xlii. book and xxx. chapter of his history, thought themselves justified in declaring war against Perseus, King of Macedon, unless he gave satisfactory proof, that he had no hostile intentions against them, in the naval and military armaments, which he was preparing. And we are informed by the same historians, that the Rhodians urged it as a rule established by the laws and customs of all civilized states; that if any one wished the destruction of an enemy, he could not punish him with death, unless he had actually done something to deserve it.