POTandESS · Potentiality and Essence: An Integrated Actualist Theory of Metaphysical Modality

Potentiality and Essence: An Integrated Actualist Theory of Metaphysical Modality

Can I get to the airport in time to catch my flight? Can we stop catastrophic climatic changes, or is this now impossible? Our lives are shaped by the answers we give to such modal questions––questions of possibility and necessity. Modality, such as necessity or possibility, is also pervasive in all areas of philosophical and scientific inquiry: our understanding of causation, laws of nature, as well as responsibility and agency crucially depend on our understanding of what must or might happen. And yet, the nature of possibility and necessity remains mysterious. In virtue of which facts are certain truths necessary, while others are merely possible or contingent? The main aim of my project is to study the sources of modality –– that is, to answer the question "in virtue of what are some things possible, impossible, or necessary?" From the late '50s and '60s the study of modality has been shaped by the crucial achievements in formal logic, and in particular by the framework of possible worlds semantics developed by Ruth Barcan Marcus and Saul Kripke. Since then, metaphysical investigations concerning the nature and source of modality have focussed on the status of possible worlds. More recently, however, a new wave of theories of modality has come to the fore. These theories all eschew talk of possible worlds –– or, at least, do not think that the sources of modality are to be found in the goings-on at such mysterious entities. Rather, they attempt to locate the sources of possibility and necessity in actual, concrete phenomena. Two theories have generated particular interest in the few years: Dispositionalism and Essentialism. The central idea of Dispositionalism is that the world is populated by irreducibly dispositional properties –– that is, properties like fragility or flammability, which alone determine the possible behaviours of their bearers –– and that these can directly explain what is possible and what is not; necessity is determined by the absence of the relevant potentialities or dispositions. It can be roughly stated as follows: (D◇) ‘possibly p’ is true iff and because there is something that has a power to p. On the other hand, the central idea of Essentialism is that entities have a nature –– that there are essential facts about them. These essential facts do, in turn, determine what is necessarily the case with regard to their bearers, and thus can directly explain what is necessary. Possibility is determined indirectly, as whatever is not ruled out by any essence. Roughly, it can be stated as follows: (E◻) ‘necessarily p’ is true iff and because there is some entities xx in virtue of whose nature p is true. Dispositionalism seems to be especially well equipped to explain the modal facts involving the dynamic evolutions of a system that essentialism struggles with—how an entity behaves—and what is possible for it to do at a later stage in time: ‘is it possible, at t, to stop the uranium pile to chain react at t*?’, ‘could I have run for another mile before stopping?’, etc. Essentialism, on the other hand, seems well suited to account for those modal facts that involve or are derived from an object’s belonging to a certain natural kind (it is in virtue of the fact that Socrates is essentially human that he is necessarily rational), the truths of logic and mathematics (it is in virtue of the nature of 2, 3, and addition that necessarily, 2+3=5), and in general facts involving timeless or synchronic relations of dependence. In short, Essentialism seems to be very apt at playing what Schrenk called the “bookkeeping” function. Both theories are still relatively in their infancy, and their face a number of yet unsolved issues. But even less studied and understood is their mutual relation. Are these theories incompatible and rivals, or can they be co-exist? Can there be a hybrid theory which incorporates elements of both? These are the central themes of my project. More specifically, I focus on three lines of inquiry: 1) Examine and evaluate each theory independently: consider its strengths and weaknesses as sole candidate for the source of modality. When confronted with problems or shortcomings of each theory, the question becomes: can they be fixed without the resources provided by the other theory? 2) Examine and evaluate the obstacles to their integration. The main main issue that stands in the way of such an integration was an argument, due to Vetter (2021), to the effect that while possibility and necessity are dual operators (they can be interdefined as follows: possibly p just is not necessarily not p), potentiality and essence seem to be, at best, semi-dual –– that is, essentially p entails not potentially not p, but not potentially not to p does not seem to entail essentially p. Conversely, potentially p entails not essentially not p, but not essentially not p does not seem to entail potentially, p. Vetter individuates three reasons to maintain that essence and potentiality are just semi-dual: their different relation to time, to objects, and to existence. I aim to examine these three cases closely, and see whether they can be dispelled.

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