The tragedy of the commons as a food basket is averted by private property, or something formally like it. The pollution problem is a consequence of population. Analysis of the pollution problem as a function of population density uncovers a not generally recognized principle of morality, namely: the morality of an act is a function of the state of the system at the time it is performed. Those who have more children will produce a larger fraction of the next generation than those with more susceptible consciences. Perhaps the simplest summary of the analysis of man’s population problems is this: the commons, if justifiable at all, is justifiable only under conditions of low-population density. As the human population has increased, the commons has had to be abandoned in one aspect after another. The man who takes money from a bank acts as if the bank were a commons.