 The barebones theory of rationality discussed above in  Section 1.1  takes an agent’s  preferences  (rankings of states of affairs) to be rational if they are complete and transitive, and it takes the agent’s choice to be rational if the agent does not prefer any feasible alternative to the one he or she chooses. Such a theory of rationality is clearly too weak, because it says nothing about belief or what rationality implies when agents do not know (with certainty) everything relevant to their choices. But it may also be too strong, since, as Isaac Levi in particular has argued (1986), there is nothing irrational about having incomplete preferences in situations involving uncertainty. Sometimes it is rational to suspend judgment and to refuse to rank alternatives that are not well understood. On the other hand, transitivity is a plausible condition, and the so-called “money pump” argument demonstrates that if one’s preferences are intransitive and one is willing to make exchanges, then one can be exploited. (Suppose an agent A prefers X to Y, Y to Z and Z to X, and that A will pay some small amount of money $P to exchange Y for X, Z for Y, and X for Z. That means that, starting with Z, A will pay $P for Y, then $P again for X, then $P again for Z and so on. Agents are not this stupid. They will instead refuse to trade or adjust their preferences to eliminate the intransitivity (but see Schick 1986).