 If it is granted that implicit knowledge of the Principles of Possibility is appropriately employed in reaching modal judgement, we can see how the judgement so reached is knowledge. Provided that any non-modal principles upon which she relies are known, a thinker’s modal judgements reached by the proper use of the implicit knowledge of the Principles of Possibility will, in the nature of the case, be knowledge. This is not only a matter of reliability. The judgement of the modal truth is explained by the thinker’s implicit grasp of principles which make the modal truth hold. (1999: 162)