Therefore, according to Plato, a just ruler should not seek war, because war is unjust. War is evil, and "The creation of evil is not an accomplishment of justice, but a failure of justice." For Plato, a just ruler, an ideal ruler would be just. He does address war, and feels the Republic should have a standing Army of trained soldiers in order to defend the Republic. Machiavelli believes the state exists to make war, and a good ruler exists for only one purpose to make war, this is his only concern.
Locke argues that man would use the goods of his labour to barter with others and appropriate different goods. No man was allowed to appropriate more than he could barter or use. Some goods were worth more than others; for example, maybe one year there is a shortage of corn but an abundance of mutton, obviously the corn has more value and the person who grew the corn therefore more wealth. Locke claims that eventually man agreed to allow a certain metal or jewel common to all, that was not perishable, serve as money to appropriate goods. Locke states "and as different degrees of industry were apt to give men possessions in different proportions, so this invention of money gave them the opportunity to continue and enlarge them" (Locke, 29).
Finally, each man, in giving himself to all, gives himself to nobody; and as there is no associate over which he does not acquire the same right as he yields others over himself, he gains an equivalent for everything he loses, and an increase of force for the preservation of what he has. (Rousseau. P.192)
In short, all the materials of thinking are derived either from our outward or inward sentiment: the mixture and composition of these belongs alone to the mind and will. Or. To express myself in philosophical language, all our ideas or more feeble perceptions are copies of our impressions or more lively ones. (Hume, David S. "Concerning Human Understanding" Section II, 13.)
A man of mild manners can form no idea of inveterate revenge or cruelty; nor can a selfish heart easily conceive the heights of friendship and generosity. It is readily allowed, that other beings may possess many senses of which we can have no conception; because the ideas of them have never been introduced to us in the only manner by which an idea can have access to the mind, to wit, by the actual feeling and sensation. (Hume, David S. "Concerning Human Understanding" Section II, 15)
as much as any one can make use of to any advantage of life before it spoils, so much he may by his labour fix a property in: whatever is beyond this, is more than his share, and belongs to others. Nothing was made by god for man to spoil or destroy. (Locke, 20)