Suppose that each is disposed to do what will be better for himself, or his family, or those he loves. There is then a practical problem. Unless something changes, the actual outcome will be worse for everyone. This problem is one of the chief reasons why we need more than laissez-faire economics—why we need both politics and morality.
We do not need them. We can not but hav them both. People are memetic creatures. There is a constant dialogue taking place between laissez faire and morality. The problem arisez when morality prevails.