 In addition to specifying what the representatives believe to be the case about the world and the results of their agreement, there must also be some standard by which the representative parties can evaluate different contractual possibilities. They must be able to rank the options on the basis of their values, whatever those may be. Rawls models parties to the contractual situation as, at least initially, having only one metric of value: primary goods. They choose the conception of justice they do insofar as they believe it will likely generate the most primary goods for them and their descendants. This specification of the evaluative parameter is uniform across choosers and therefore, choice in the original position can be modeled as the choice of one individual. Insofar as there is evaluative diversity between the representatives, more complex models of agreement will be needed (see §3). If we think in terms of decision theory, the doxastic specification individuates the initial state of affairs and the outcomes of the contractual model, while the specification of the evaluative elements gives each representative party a ranking of the outcomes expected to result from the choice of any given set of rules. Once these elements are specified, we have a model of the parties to the contract.