labour contributed". Anarcho-communism, as defended by Peter Kropotkin and Errico Malatesta, rejected the labor theory of value and exchange value itself, advocated a gift economy and to base distribution on need. Ethics of pricing Josiah Warren termed the phrase "Cost the limit of price", with "cost" here referring not to monetary price paid but the labor one exerted to produce an item. This understanding of cost is congruent with that of the classical economist Adam Smith who said: "The real price of every thing, what every thing really costs to the man who wants to acquire it, is the toil and trouble of acquiring it". However, Warren reached different conclusions as he believed that goods and services should trade according to how much labor was exerted to produce them and bring them to market, instead of according to how individuals believed them to be subjectively worth. Therefore, "[h]e proposed a system to pay people with certificates indicating how many hours of work they did. They could exchange the notes at local time stores for goods that took the same amount of time to produce". To charge more labor for something that entailed less labor was "cannibalism", according to him. Moreover, he believed that trading according to "cost the limit of price" would promote increasing efficiency in an economy, as he explains in Equitable Commerce: He put his theories to the test by establishing an experimental "labor for labor store" called the Cincinnati Time Store at the corner of 5th and Elm Streets in what is now downtown Cincinnati, where trade was facilitated by notes backed by a promise to perform labor: "All the goods offered for sale in Warren's store were offered at the same price the merchant himself had paid for them, plus a small surcharge, in the neighborhood of 4 to 7 percent, to cover store overhead". The store proved successful and operated for three years after which it was closed so that Warren could pursue establishing colonies based on mutualism. These included Utopia and Modern Times. Warren said that Stephen Pearl Andrews' The Science of Society, published in 1852, was the most lucid and complete exposition of Warren's own theories. Energy credits The theory that all values can be evaluated in terms of joules. In the same vein as the labor theory of value, this is an attempt to make a normative basis for value by accounting