"for one man to take something from another and to increase his own advantage at the cost of another’s disadvantage is more contrary to nature than death, than poverty, than pain and than anything else that may happen to his body or external possessions. In the first place, it destroys the common life and fellowship of men: for if we are so minded that any one man will use theft or violence against another for his own profit, then necessarily the thing that is most of all in accordance with nature will be shattered, that is the fellowship of the human race. Suppose that each limb were disposed to think that it would be able to grow strong by taking over to itself its neighbour’s strength; necessarily the whole body would weaken and die. In the same way, if each one of us were to snatch for himself the advantages other men have and take what he could for his own profit, then necessarily fellowship and community among men would be overthrown. It is permitted to us – nature does not oppose it – that each man should prefer to secure for himself rather than for another anything connected with the necessities of life. However, nature does not allow us to increase our means, our resources and our wealth by despoiling others."
- Cicero, On Duties, III.21-22