is 'market value', or 'willingness to pay', the principal method of accounting used in neo-classical economics. In contrast, both Marx's labour theory of value and the emergy concept are conceived as donor-type value. Emergy theorists believe that this conception of value has relevance to all of philosophy, economics, sociology and psychology as well as Environmental Science. Silvio Gesell denied value theory in economics. He thought that value theory is useless and prevents economics from becoming science and that a currency administration guided by value theory is doomed to sterility and inactivity. See also Aesthetics Anthropological theories of value Axiological ethics Baden School Cultural Institutions Studies Graded absolutism Illegalism Intuitionism Labor theory of value Law of value Logic Morality Friedrich Nietzsche Normative science Practical philosophy Pirsig's Metaphysics of Quality Rationality Rationality and power Social contract Summum bonum Thick concept Ultimate importance Value-added theory Value engineering References Further reading Nicholas Rescher. 2010. Axiogenesis: An Essay in Metaphysical Optimalism. Lexington Books. Value (ethics) Axiological theories it:Teoria dei valori zh:價值觀