distribution setting the stage for the formation of an extreme majority. 

## Subjective Probability as Rhetorical Issue 

We elaborate upon the nature of the rhetorical function in the context of decision making under risk and uncertainty (Pleskac, Diederich, and Wallsten 2015). Consider an event with two exclusive outcomes — for example, whether a nation’s economy will grow or contract or the winning candidate in an election — of primary importance to a policy decision such as the level of an investment. Group members, even if they have identical utilities with respect to the value of an outcome, may differ as to their assessments of the probability of that outcome and hence prefer different policies. The rhetorical issue upon which policy discussion is focused is then the outcome probability estimate. In modern theories of decision making, such as prospect theory, not only is utility generally a nonlinear function of wealth (as in classic expected utility theory) but the weights used to combine outcome utilities are also nonlinear functions of probability (reflecting psychological tendencies to over or under-weight probabilities) (Wakker 2010). Consequently, the relationship between the subjective probability and the optimal policy will, in general, be nonlinear. 

We take the rhetorical issue to be the subjective probability estimate of one of the two outcomes in a binary gamble. When the stakes are small, then an individual’s wager will not only increase with their subjective probability estimate but do so at an accelerating rate. As we show in the Supplementary Material, this convex (upward curving) dependence of wager upon probability arises under both expected utility and prospect theories using an exponential form of the utility function and so is quite general (Wakker 2010:80-81). 2 The rhetorical function, however, is how the rhetorical issue depends upon the policy. The convex dependence above then 

