 Some forms of contractualism explicitly favour ex ante rather than ex post evaluation. Rawls, for instance, asks his parties to choose principles to govern their society on the basis of general knowledge about how their lives might go, rather than particular information about their specific circumstances. Scanlonian contractualism, by contrast, usually requires justification to actual people who are aware of their own situation. In his 1998 book, Scanlon explicitly favours ex post justification. However, most contractualists (including Scanlon himself) now favour either ex ante contractualism or some hybrid view combining both ex ante and ex post evaluations. (Scanlon 2013, Kumar 2015, Frick 2015.)