Jonathan Nassim

Cases of grounding failure present a puzzle for fundamental metaphysics. Typically, solutions are thought to lie either in adding ontology such as haecceities or in re‐describing the cases by means of the ideology of metaphysical indeterminacy. The controversial status of haecceities has led some to favour metaphysical indeterminacy as the way to solve the puzzle. We consider two further treatments of grounding failure each of which, we argue, is a more plausible alternative. As such, the initial dichotomy is a false one, and these alternative options deserve consideration before resorting to the heavyweight machinery of metaphysical indeterminacy.

Throughout his career, Keith Hossack has made outstanding contributions to the theory of knowledge, metaphysics and the philosophy of mathematics. This collection of previously unpublished papers begins with a focus on Hossack's conception of the nature of knowledge, his metaphysics of facts and his account of the relations between knowledge, agents and facts. Attention moves to Hossack's philosophy of mind and the nature of consciousness, before turning to the notion of necessity and its interaction with a priori knowledge. Hossack's views on the nature of proof, logical truth, conditionals and generality are discussed in depth. In the final chapters, questions about the identity of mathematical objects and our knowledge of them take centre stage, together with questions about the necessity and generality of mathematical and logical truths.

We examine a contribution L. Susan Stebbing made to the understanding of critical thinking and its relation to formal logic. Stebbing took expertise in formal logic to authorise logical intervention in public debate, specifically in assessing of the validity of everyday reasoning. She held, however, that formal logic is purely the study of logical form. Given the problems of ascertaining logical form in any particular instance, and that logical form does not always track informal validity, it is difficult to see how she could justify her belief in logical interventionism. Her answer to this problem is the contribution we explore here. It involves the view that although the logician’s expertise is not sufficient to assess arguments made in everyday contexts on its own, it nevertheless plays a unique role in giving systematicity and direction to the critique of such arguments, in particular, in public debate.

This thesis is an argument for the view that there are problems for Modal Reductionism, the thesis that modality can satisfactorily be defined in non-modal terms. I proceed via a case study of David Lewis’s theory of concrete possible worlds. This theory is commonly regarded as the best and most influential candidate reductive theory of modality. Based on a detailed examination of its ontology, analysis and justification, I conclude that it does badly with respect to the following four minimal conditions on a satisfactory reductive theory of modality: that it be (a) genuinely reductive, (b) materially adequate, (c) conceptually adequate and (d) that its justification provides good reason to think it true. These problems for Lewis’s theory are not, I suggest, due to his idiosyncratic conception of possible worlds as concrete entities. Rather, because Lewis’s theory can be seen to represent an important class of structurally similar reductive theories of modality, the problems for Lewis’s theory generalise to problems for these other theories. This suggests that Modal Reductionism is unpromising. In the light of this, the alternative approach to understanding modality, Modal Primitivism, appears more attractive.