The Power of Powers: Dispositions, Essences, and Laws of Nature
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- Department of Philosophy 
This thesis aims to articulate a dispositionalist theory of possibility. The standard way of explaining possibility, and modality in general, is by reference to possible worlds. At the same time, discontentment with possible worlds and their role in the metaphysics of modality has been present in the literature at least since Kripke. The later years this scepticism towards possible worlds has been voiced by a group of philosophers known as ‘new actualists’. They generally support a view of modality not based upon possible worlds while displaying a more positive attitude towards concepts like dispositions, powers, and potentials. My project shares this attitude towards the metaphysics of modality, and the aim of this thesis is to explain modality, particularly possibility, by referring to this world only. That is, I will ask what, in the actual world, substantiate the truth of modal claims. The solution defended in this thesis, dispositional essentialism, takes as a starting point a particular subset of dispositional properties. I refer to these properties as powers, or dispositional essences, and they are defined as sparse, fundamental properties which are essentially dispositional—and electrical charge can serve as a good example. There are two positive aspects of assuming powers to be existing. Firstly, we get an account of property identity at the fundamental level. We may say that the distinction between what these fundamental properties are and what they do is removed, so what it is to be a certain property becomes equivalent with what it is disposed to do. Thus, the dispositionality present in the world goes ‘all the way down’ to the most fundamental level where there is no further structure to appeal to. There is no need to ground dispositions in ‘respectable categorical properties’, because dispositions are respectable entities in themselves. Secondly, this account of fundamental properties yields automatically an account of the laws of nature. The fundamental laws are now grounded in the essential relations between fundamental properties. This means that we, by assuming powers to be a part of our ontology, gain an account of laws which is more parsimonious than what the competing views offer, since these competing views will need an account of laws in addition to an account of fundamental properties. Assuming powers to exist gives us both of these things at once. However, another consequence of assuming powers to exist is that relations between fundamental properties will have to be seen as necessary, because these relations are given by the essences of these properties—they could not have been different. This entails one particularly important consequence for the accounts of laws based upon powers: the laws of nature will have to be seen as absolutely, metaphysically, necessary. This, in turn, influences what is deemed possible, since what is possible is limited by the laws of nature. Hence, in my account the domain of the possible is radically diminished, as compared to other accounts of possibility and the laws. This is generally perceived as a problem for the dispositional essentialist, because it collides with our intuition that the laws of nature are contingent, and that happenings going beyond the laws of nature, metaphysically could happen. That is, we may say that, for the dispositional essentialist, the metaphysical modalities collapse into the nomic. Our grounding of possibility in the properties of the actual world gives us a domain of the possible which is consistent with the laws of nature. We do not have grounding for possibilities going beyond this; there is nothing in the world in which these alleged possibilities may be grounded. Thus, we see that the dispositional essentialist view of the fundamental properties of the world is radically different—particularly when it comes to the idea of nomic change— from views advocated by defenders of Humean supervenience. We can get a rough idea of this difference by considering the following illustration. Humean accounts of fundamental properties are often visualised by speaking of the ‘Humean mosaic’. Yet, as I shall argue, the powers theorist can in a similar fashion speak of the ‘dispositional essentialist web’. These metaphors make the difference between the two views especially clear. Where the removal of a tile in a complex mosaic floor might lead to minuscule change, perhaps not even noticeable, removing a thread from a web has a much more dramatic effect; the web unravels. If we accept that possibility and the laws of nature are closely related in the way I described, this gives us a third reason to assume powers to be existing. Powers will— through their capacity to determine the laws of nature—also constrain possibility. Accounts of possibility in terms of dispositions have become popular lately, but I hold that some of the assumptions made by some of the proponents of these accounts—such as the expectation that dispositional accounts of possibility can deliver genuine possibilities going beyond the laws of nature—are problematic. Thus, we are better off by explaining possibility by referring to powers and not mere dispositions. However, an account of possibility in terms of dispositional essences will perhaps seem less impressive than a more general dispositional account of possibility, since it is not able to directly explain each and every possibility in the world. However, I argue that we will have to settle for an explanation of what generates possibility. The hope is still that such an account of property identity, laws of nature, and possibility will fare better than any competing view, because of its parsimony and its closer connection with science. Finally, we need to note that because of the discrepancies between our intuitions about the laws of nature on the one hand, and the view advocated by the dispositional essentialist on the other (who holds these laws to be necessary), accepting dispositional essentialism entails that we need to defend our distrust of intuitions in this case. Hence, an additional aim of my thesis is to show that the necessity of the laws of nature is not a ‘bug’, but rather an attractive feature of dispositional essentialism.