Jan Krajìček, Proof Complexity, Encyclopedia of Mathematics and Its Applications, no. 170, Cambridge University Press, Cambridge, UK, 2019, xvi + 516 pp.

and ‘??’ is a subjective catch-all standing in for those contingencies that she suspects she is unaware of. Represented like this, Steele and Stefánsson argue that the policy-maker’s predicament is somewhat unremarkable and (if certain basic conditions are met) we can treat her as an EU maximiser just like any ordinary reasoner. However, they go on to canvas two norms of rationality—‘Awareness Reflection’ and ‘Preference Awareness Reflection’—which they think should constrain the synchronic credences and desires (respectively) of agents like the policy-maker who anticipate their awareness will grow in rather specific ways. Whilst the positive proposal spelled out in Sections 6 and 7 leaves several questions open, Steele and Stefánsson successfully lay the foundations for others working within normative decision theory and related areas of economics and computer science to take up these questions and continue the work of characterising the reasoning of rational, but less-than-fully aware, agents.