The nature of capitalism is criticized by left-wing anarchists, who reject hierarchy and advocate stateless societies based on non-hierarchical voluntary associations. Anarchism is generally defined as the libertarian philosophy which holds the state to be undesirable, unnecessary and harmful as well as opposing authoritarianism, illegitimate authority and hierarchical organization in the conduct of human relations. Capitalism is generally considered by scholars to be an economic system that includes private ownership of the means of production, creation of goods or services for profit or income, the accumulation of capital, competitive markets, voluntary exchange and wage labor which has generally been opposed by anarchists historically. Since capitalism is variously defined by sources and there is no general consensus among scholars on the definition nor on how the term should be used as a historical category, the designation is applied to a variety of historical cases, varying in time, geography, politics and culture. Anarcho-capitalists believe that capitalism is the absence of coercion and therefore fully compatible with the philosophy of anarchism; they claim that an effort to put a stop to what they consider "voluntary hierarchy" is inconsistent with the philosophical tradition of "freedom" present in anarchist thought. Some argue that anarcho-capitalism is a form of individualist anarchism, although this has been contested or rejected, including an individualist–socialist divide. Many others deny that anarcho-capitalism is a form of anarchism at all, or that capitalism is compatible with anarchism, seeing it as a form of New Right libertarianism. Anarcho-capitalist author and theorist Murray Rothbard, who coined the term itself and developed such philosophy from the 1950s through the 1970s, stated that individualist anarchism is different from capitalism because the individualist anarchists retain the labor theory of value and socialist doctrines. Anarchist commentators do not consider anarcho-capitalism as a legitimate form of anarchism due to perceived coercive characteristics of capitalism. In particular, they argue that certain capitalist transactions are not voluntary and that maintaining the class structure of a capitalist society requires coercion in violation of anarchist principles. Anarchist criticism of capitalism and economic issues It has been pointed out that historically the anarcho-communist economic theories published by Peter Kropotkin and others have been ignored or intentionally sidelined by historians. Anarchists such as Kropotkin object to the portrayal of economics as a value-free science, arguing in Revolutionary Pamphlets: Within the realm of anarchist labor issues is the issue of the monetary system. While all anarchists