We continually make decisions in private which affect the commonweal, as the ecologists (to take but one example) have shown us. When I keep my house warmer than it needs to be, I consume fuel which might help someone else keep warm, or keep a job. When the food I eat is high on the protein chain I contribute to a maldistribution of protein around the world. When I teach my children to be primarily concerned with private gain, I diminish the ranks of public leadership in the rising generation.
