According to Adam Smith, self-interest benefits society since:
It causes people to behave more cautiosly.
The underlying concept behind self-interest in economics, is the one of "the invisible hand" introduced by Adam Smithin 18th century. It basically means that when economic actors make economic decisions, based on self-interest, this unintendedly benefits society as a whole. As a consequence, decisions are made cautiosly (because people act <u>rationally)</u>, meaning that, for instance, a family (demand) will adjust their consumption according to the prices, seeking to consume more at lower prices, the same way as, on the other hand, businesses (supply) will seek to obtain maximum benefits at the lowest cost possible.
It's because then they would have a higher chance of winning WW1 since if they have unified all together between that time they would be much stronger together overall.
