The reality of what actually is exchanged is concealed by our one-dimensional concept of money, where the same currency serves as a unit of account and as a universal means of payment. The spreading use of electronic purses allows us to design a currency with four dimensions, measuring the quantity of labor used within a given territory, the quantity of labor supplied from the outside; the amount of fossil energy and of non-renewable natural resources. The very nature of fossil energy invites us to distribute the right to use it according to individual quotas, negotiated first at the scale of a territory then, step by step, up to the planetary scale.