The Anti-Utopianism of Private-Property Anarchism
"As a reflection of this fundamental realism—anti-utopianism—of his private-property anarchism, Rothbard, unlike most contemporary political philosophers, accorded central importance to the subject of punishment. For him, private property and the right to physical defense were inseparable. No one can be said to be the owner of something if he is not permitted to defend his property by physical violence against possible invaders and invasions.
—Hans-Hermann Hoppe's Introduction to Murray N. Rothbard's The Ethics of Liberty