 The money-pump argument relies on a particular, far from uncontroversial, way to combine preferences in two dimensions, which is only possible if two crucial assumptions are satisfied: (1) The primary alternatives (the stamps) can be combined with some other commodity (money) to form composite alternatives. (2) Irrespectively of the previous transactions there is always, for each preferred change of primary alternatives, some non-zero loss of the auxiliary commodity (money) that is worth that change. The money-pump can be used to extract money from a subject with cyclic preferences only if these two conditions are satisfied.