McKitrick (2003) famously challenged the thesis that all powers are intrinsic properties of their bearers, providing some examples of extrinsic dispositions, such as weight, vulnerability, visibility and recognizability. According to her view, the Intrinsic Dispositions Thesis (IDT) cannot be taken as an exceptionless universal principle for the possession of dispositions. Bird (2007, p. 30) pointed out that the dispositions advanced by McKitrick are all examples of non-sparse properties. Bauer (2011) attempted to overcome this limitation, by arguing that ‘mass’, an indubitable sparse property, is a disposition extrinsically grounded in the Higgs field. More recently, Vetter recognized the existence of some extrinsic potentialities, even though being “entirely derivative” from intrinsic ones (2015, p. 125). In sum, if the IDT is not today considered to be an exceptionless universal principle, at the very least it is taken to be the rule or paradigm. Our goal is to argue for the opposite view.
In particular, we shall argue that the Extrinsic Dispositions Thesis (EDT) applies to all powers whose manifestation necessarily depends on the obtaining of some causal relation between their bearers and some external entities. Solubility, fragility, and flammability are clear examples of such powers. We shall call them ‘relational causal powers’ (RCPs). According to the proposed argument, the individuation and real definition of any RCP necessarily involves a reference to some specific causal relations between the bearer of the RCP and some specific external causal co-relata, for only relative to some causal relations with some external co-relata is an RCP a real power for its manifestation. Consequently, only through some causal relations with some external co-relata can the bearer of an RCP manifest that RCP – even if it never manages to actually do so. This means that every RCP is a complex, extrinsic relational property, its instantiation thus implying the instantiation of its constitutive co-relatum, as well as the existence of its constitutive relation as a possible relation.
Sugar’s solubility power is its power to be dissolved only by being immersed in some solvent. Only that kind of interaction (viz., immersion) may bring about the manifestation of that power. But that is not enough. Sugar’s solubility power is not its power to be dissolved by being immersed in any kind of substance, nor even in any kind of solvent. Aqua regia is a solvent, but it does not have the power to dissolve sugar. Aqua regia has the power to dissolve some noble metals, such as gold and platinum, but not iridium, nor silver. Sugar’s solubility power is its power to be dissolved only through its immersion in some solvents, such as water. Water has the power to dissolve sugar, but it does not have the power to dissolve noble metals. The real-world solubility power that a sugar cube has is its power ‘to be dissolved by some solvents such as water’. A hammer has the power to break things like glass cups, but not things like atoms. Metallic hydrides are not flammable relative to water or oxygen, for they simply don’t have the power to undergo combustion by interacting with things like water or oxygen. No negatively electric charged particle has the power to attract other negatively electric charged particle. The real causal powers possessed by a negatively electric charged particle are the powers ‘to attract positively electric charged particles’ and ‘repel other negatively electric charged particles’.
According to the received view, all powers, or at least the great majority of them, are either intrinsic or reducible to intrinsic ones. Naturally, this conviction applies also to fundamental physics: the fundamental physical properties are all intrinsic. As Molnar says, “according to basic physical theory, the subatomic particles have a limited number of essential properties, all of which are intrinsic, basic, and prima facie dispositional” (2006, p. 108). In the second part of our talk, we will challenge this view, both in philosophical and physical terms. In this sense we will analyse and discuss the intrinsicality/extrinsicality of some of the properties instantiated by the fundamental physical entities, such as electric charge, colour charge and spin.

References
Bauer, William (2011). An Argument for the Extrinsic Grounding of Mass. Erkenntnis, 74, 81-99.
Bird, Alexander (2007). Nature’s metaphysics: laws and properties. Oxford: Oxford University Press.
McKitrick, Jennifer (2003). A Case for Extrinsic Dispositions. Australasian Journal of Philosophy, 81(2), 155-174.
Molnar, G. (2003). Powers: A Study in Metaphysics. Oxford: Oxford University Press.
Vetter, Barbara (2015). Potentiality: From dispositions to modality. Oxford: Oxford University Press.