Gideon Rosen

We know a great deal about what is possible, so modal knowledge must be possible, not just in principle but by ordinary methods. Christopher Peacocke’s leading thought in Chapter 4 of Being Known is that this fact places significant constraints on philosophical treatments of modality. Modal realism is ruled out on the ground that it renders modal truth “radically inaccessible”, and actualism is forced upon us. It goes without saying that any account of the modal facts must eventually dovetail with some account of how we know them. But Peacocke’s approach is animated by the thought that there is a mystery about modal knowledge—a transposed version of Benacerraf’s puzzle about mathematical knowledge under Platonism. Peacocke clearly believes that modal realism renders the problem intractable. But what exactly is the mystery in the modal case? And why exactly does modal realism preclude a solution? Peacocke himself does not say. The ‘access problem’ for modal realism is clearly decisive for him; but it is very much in the background. Nonetheless, for several reasons, it will help to start here.

The paper examines the conditions under which we are responsible for actions performed under duress, focusing on a real case in which a soldier was compelled at gunpoint to participate in the massacre of civilian prisoners. The case stands for a class of cases in which the compelled act is neither clearly justified nor clearly excused on grounds of temporary incapacity, but in which it is nonetheless plausible that the agent is not morally blameworthy. The theoretical challenge is to identify the excuse in such cases and to explain its basis. The paper argues that when mortal duress excuses in cases of this sort, it does so because the compelled act, though impermissible and freely chosen, nonetheless fails to manifest ‘an insufficiently good will’. The argument depends on a potentially controversial thesis in the ethics of concern, namely, that a thoroughly decent moral agent—someone who cares enough about morality and the values that underlie it—will not always be moved to do what he knows he ought to do.

Fictionalism about possible worlds is the view that talk about worlds in the analysis of modality is to be construed as ontologically innocent discourse about the content of a fiction. Versions of the view have been defended by D M Armstrong (in "A Combinatorial Theory of Possibility") and by myself (in "Modal Fictionalism', "Mind" 99, July 1990). The present note argues that fictionalist accounts of modality (both Armstrong's version and my own) fail to serve the fictionalists ontological purposes because they imply that as a matter of necessity there exist many worlds