4. Conclusion
In the classical circular conception of the economy, the value of the ecosystem's goods and services can be seen in terms of their contribution to the circular process of socio-economic reproduction, and measured in terms of the physical inputs that constitute the cost of production, including the basic commodities that lead to the achievement of a certain standard of living that can be discussed through a public debate undertaken with (positional) objectivity. The key question to address, as it was for the classical authors, concerns whether the surplus, that is, the part of production above whatever is necessary for achieving a certain standard of living, is distributed and used (indeed, recycled) in an efficient way, or whether it merely creates economic waste (that is, wasteful luxurious consumption, which was much criticized by the classical authors), and physical waste (with negative impact on ecosystems). The circular conception of the economy provides only a basis for further exercises in valuation, rather than an algorithmic model of valuation. But in so doing, it already provides a positive contribution, to the extent that it sets the debate in terms of the circular nature of the process of reproduction (rather than in a linear nature aimed at satisfaction of subjective preferences) while stressing the distinction between natural resources and manufactured capital in the very core of its theory of value (rather than focusing on aggregate capital). The distinction between rent and profits, an expression of the difference between natural resources and manufactured capital, provides a theory of value where scarcity is seen as a specific property of natural resources and studied in connection to strong sustainability.