Welfare economics

Since all State actions rest on the fundamental binary intervention of taxation, it follows that no State action can increase social utility, i.e., can increase the utility of all affected individuals.

... says Rothbard in Man, Economy and State (chapter 12), defining "binary intervention" as an intervention where

the intervener may compel an exchange between the individual subject and himself or coerce a “gift” from the subject

and which is

exempli­fied in taxation, conscription, and compulsory jury service. Slavery is another example of binary, coerced exchange between master and slave.

For a more detailed analysis, Rothbard refers to his own Toward a Reconstruction of Utility and Welfare Economics, which I call a must-read for all those interested in the philosophy of State coercion. It ends with the following lines:

Economics by itself and standing alone cannot establish an ethical system, and we must grant this regardless of what philosophy of ethics we hold. The fact that the free market maximizes social utility, or that State action cannot be considered voluntary, or that the laissez-faire economists were better welfare analysts than they are given credit for, in itself implies no plea for laissez-faire or for any other social system. What welfare economics does is to present these conclusions to the framer of ethical judgments as part of the data for his ethical system. To the person who scorns social utility or admires coercion, our analysis might furnish powerful arguments for a policy of thoroughgoing Statism.

Indeed!