Context:

More specifically, income here means taxing the annual rental value of natural resources and (if we can’t comfortably get rid of them) any other privilege that grants monopoly power to its owner by way of no one else being able to reproduce and compete with that power.

The issue with taxing the income of labor and capital is that it stymies the reward of producing and providing for others, discouraging we as a society from doing exactly that. At the same time, the issue with privatizing the income of land and other monopolistic assets is that it encourages people to treat them as an investment, one that doesn’t add to the economy but extracts wealth from it by way of monopoly power.

The best way to reward people for producing and providing for others is to untax the work or investment they put in, while taxing/mitigating land and other monopolistic assets to prevent them from being turned into a tool for wealth extraction.