 The probability triangle affords a helpful illustration of the incompatibility of the Allais preferences with SEU. Indeed, the segments connecting \(P_1\) and \( P_2\), on the one hand, and \( P_3\) and \(P_4\) on the other are parallel, so that an EU maximiser, whose indifference curves are also parallel, would be incapable of exhibiting the modal preferences, since no pair of indifference curves could be, as required, such that one crosses the segment \([P_1,P_2]\) from below while the other crosses \([P_3,P_4]\) from above: