argue that a single tax on the rental value of land, typically in conjunction with Pigovian pollution and severance fees to internalize negative externalities and curb natural resource depletion, is not only non-distortionary and politically sustainable but also more ethically attractive than zero taxation and even required for justice in property rights. Voluntary slavery Libertarians generally believe that voluntary slavery is a contradiction in terms. However, certain right-libertarians dispute the Lockean claim that some rights are inalienable and maintain that even permanent voluntary slavery is possible and contractually binding. Famous libertarian Murray Rothbard argued that libertarians seeing children as property of the parents left the platform open to sales of children as slaves, when parents needed finances, and that people entering into voluntary slavery would most likely be when there was no alternative available to pay debts, but this was not coercive as under the libertarian platform only the government could engage in coercion. Detractors maintain that there is no such thing as a morally-binding "slavery contract". Involuntary psychiatry Involuntary commitment, outpatient commitment, and involuntary treatment, although in opposition to self-ownership and in some countries the main way of confinement and social control are issues rarely discussed by libertarians. Thomas Szasz argues that involuntary psychiatry is incompatible with libertarianism and that Bertrand Russell, Robert Nozick, John Stuart Mill, Ayn Rand, The American Civil Liberties Union, and Friedrich von Hayek among other "went wrong" by their omission, ambiguity or direct support. Most criticism comes from fields such as sociology (such as Michel Foucault), psychiatry (such as Franco Basaglia), human rights NGOs or philosophy and public position by libertarians are often uncertain. Strategy Non-voting Some libertarians such as agorists employ non-voting as a political tactic and following 19th-century individualist anarchists like Lysander Spooner and Benjamin Tucker consider voting an immoral concession of state legitimacy. Others who champion the concept of rational ignorance view voting as an impractical and irrational behavior on a cost-benefit analysis. Other more moderate libertarians abstain from voting to voice their feeling that the current system is broken or out of touch. Apart from principled and cynical non-voters, many libertarians interpret voting even for a suboptimal candidate or policy as an act of political self-defense aimed at minimizing rights violations. Political alliances Until fairly recently, American libertarians have allied politically with modern conservatives over economic issues and gun laws while they are more prone to ally with liberals on