WHAT ARE CAUSAL POWERS
University of Nottingham
"Metaphysics of powers offer an alternative approach to the
problem of causation. It is argued that this approach, causal
dispositionalism, is explanatory of the behaviour of biological
systems and artefact in terms of their causal production. This
behaviour is a function of selection between natural
possibilities that powers support and constrain."
1. Dispositional Properties According to dispositionalism, causation is produced by the exercise of causal powers. The reason why dispositional properties are often called powers is to highlight their causal role. Dispositions inhere in the object of dispositional ascription. The causal in causal powers is the fact that their exercise is productive of the behaviour of things. Dispositions are not mere potentialities. Their manifestations do not depend on the presence of an active stimulus. To say that something is soluble is not to think that the property is instantiated only when the dissolving occurs (Mumford 1998). Dispositions are active, but they produce the effect by composing together with other dispositions. Causation as mutual manifestation partnership explains the effect as the change in powers when they team up. This starts a causal process that is diachronical, with which we can interfere and that have as effect a modification of the causal scenario. 2. Causal production The exercise of dispositions represents causal production. For dispositionalism individuals have their own causal powers and any effects exhibited are the manifestation of those powers. But objects possess dispositional properties even if those are not manifested. To say that dispositional property is a property that can exist unmanifested means that it points to hidden potentials of objects. A dispositional theory of causation sees discovery in the sciences as the exploitation of causal powers, and achievements in technology as the ability to use objects' hidden dispositional properties to build systems specifically designed to support a constrained set of possibilities. Causation as the passing around of powers depicts hidden potential as a disposition for the instantiation of another possible causal property. That which is soluble has the potential to become dissolved (Mumford 2009). Causation explains the activity of individual objects in virtue of their dispositional properties. Most of the complex biological interactions that dispositionalism claims to explain involve causal interaction. (a) Not all the causal interactions are also functional (in the sense explained below). Then how can a functional account be given of dispositions? 3. Dispositionality as selection function [Note: 'function' here, is used not in the teleological sense, in which biological organs have functions, but in the mathematical sense in which a function given an argument selects values from a range of possible values.] The idea of a selection function is meant to explain that when powers are exercised a subset of realm of possibilities is selected, favouring some among others. Changes in dispositional properties are explained in terms of selection from a range of natural possibilities (Mumford&Anjum 2011). The exercise of powers provides the object with abilities to interact causally with the world, linking sets of possible changes. The modal space available to the object is marked by a set of possible causal links between natural possibilities (Sloman 1996). Dispositional ascription allows causal explanations of behaviour of natural things. Since dispositionality selects natural possibility, not logical possibility, when powers are exercised we often know what to expect. But dispositionality acts between pure contingency and pure necessity. A disposition only tends toward its manifestation, but does not necessitate the effect. We make sense of ascribing a dispositional property to an object without implying that the manifestation is necessitated 3.1 Compositional pluralism and directness The same disposition can be manifested differently in response to the presence or absence of other powers at work. Compositional pluralism is the claim that there are pluralities of ways in which powers can compose to produce an effect. When they team up they alter each other's contributions to the causal outcome (Mumford&Anjum 2011). That a vase is fragile means there are possible ways in which the vase can be damaged: it can be struck by a hammer, pushed to the ground or smashed against the wall. There are also possible ways in which the vase can tend to break: it can break into a few pieces, or tiny fragments, or be burned to dust by a laser. Also a piece of metal could be fragile. However for the fragility of metal to be manifested requires that other causal powers are in place. For instance, diminish the temperature of the object beyond a certain threshold and it will become as fragile as a vase. Dispositionality explains objects' modal facts that are effects of the powers' control over potentialities. Powers act as a whole, at different levels of reality. A kiss may cause embarrassment, as well as energy transfer between bodies. A cube of sugar can be disposed to dissolve in water, as well as sweetening the solution. (b) Which of these types of directness can be considered functional? (i.e. selecting from a set of possibilities.) 3.2 Getting functional Functional Dispositionalism assumes that things in nature generate, maintain and develop their own modal space and powers are causal in that they constrain possible changes as causation occurs. An object's dispositions depend on what natural possibilities are at hand; and which outcome is brought about depends on which functional role (which ability to select among possibilities) is instantiated. It is not obvious what it is for a disposition to be a function in this sense. A common assumption of dispositional ascription and functional ascription is that both endorse a function/accident distinction. Within this distinction the sweetened solution is an accidental effect of the functional power of the solubility of sugar (Wright 1976). "Dispositional" and "functional" are ascriptions that are always relative to a choice of explanandum (what is to be explained) (Wright 1973). (c) Then, is the claim that dispositional ascriptions are functional ascriptions informative? When we ascribe a disposition we are giving a functional characterization of the property, according to what potentialities are supported in various causal contexts. For something to be elastic means to have a dispositional properties that cause it to stretch when pulled and to shrink when the pull is removed. We functionally characterize this disposition in terms of elasticity. Dispositional ascriptions are explanatory when they indicate what potency is present in the object of ascription. The functional characterization of this property does not exclude the same disposition from manifesting other effects accidentally. Dispositionality as selection function implies possible changes in the composition of powers. To ascribe a disposition to an object is to say something about what the object can do, within its modal space, not how it organizes it. To say that A and B mutually manifest C is not to say how A and B compose C. The dispositionalist claim is informative in that it suggests that dispositions are particular kinds of functions (selections) (Mumford 1998). If an object exhibits a function it is because the object has the ability to do that. And to have ability is to have a disposition. Nonetheless a dispositional ascription just specifies that a causal contribution has a functional (selective) role, but leaves open how the contribution is integrated when other powers contribute to realizing the function. 4. Dispositionality and Complexity (d) The realization of a function requires more than possession of a disposition. The modality of the system is represented as a selection function that acts on various dispositions whose manifestations work toward a common end-state. It is because a disposition is a particular kind of function that we can admit the production of non-functional changes. For instance, the appearance of an adaptive trait in an organism is strongly coupled with the manifestation of non-adaptive traits. However those traits might reveal themselves functional during an organism's development (Nagel 1979). For powers to instantiate a function they must be organized appropriately. Only when causal powers of many components are brought together in the right arrangement are hidden potentialities supported, e.g. a bridge. When we pull ends of a climbing rope apart, that could provide a new pathway to an end-state. There could be knots forming that affect how the rope can be pulled. Its wetness can affect how the rope curls. A wire has a disposition to conduct electricity. But cooling down a piece of metal and same dispositions manifest superconductivity, together with the ability to store energy. With appropriate causal factor it can dispose toward making light. Where processes develop, different constraints on possibilities might emerge and affect the paths to the end-state. Those constraints are better understood as changes in complexity, affecting the way dispositions can compose together. In complex systems functions always involve dynamically varying causal inputs that are selected toward a casual output, each of those modulates each other effect. The ways components are organized have effects upon the selection function, causing a change in complexity, both compositional and dynamical. Functions in systems are involved with possible interactions that change possibility between parts. We can join two wires in parallel and their voltage is constrained to be the same. When joined in series, the same happens to current. In both cases, the disposition ascribed to the system could not be reduced to the sum of the powers of the components. Two wires coupled in a diode compose a complex object whose functional characterization cannot be reduced to the sum of functional characterization of component properties. Functional dispositionalism can accept physicalism without implying reductionism since powers act at different levels of complexity. 4.1 Adaptive Emergence (e) Exercise of powers regulates the selection of naturally possible outcomes with respect to interference in the causal ecosystem in which the system behaves. Functional systems are responsive to causal ecosystem in which they behave. A functional account of dispositions can help investigate emergent abilities of biological systems in terms of adaptive response to environmental influence. Organization only disposes toward the end-state since systems behaviour is brought about by different dispositions working together. Dispositional ascription instantiate more than one functional role concurrently. The adapting feature of powers composition can represent a step toward the explanation of emergent change in complexity: evolved complexity (Mitchell 2003). This complex feature of biological systems can be interpret as incremental constrain over the modal space generated by causal development. References Mumford, S. & Anjum, R. L., (2011). Getting Causes from Powers. OUP Oxford. Mumford, S., (1998). Dispositions. Oxford University Press. --- (2009). Passing Powers Around. The Monist 92 (1):94-111. Mitchell, S., (2003). Biological Complexity and Integrative Pluralism. Cambridge Univ Pr. Nagel, E., (1979). Teleology Revisited and Other Essays in the Philosophy and History of Science. Columbia University Press. Sloman, A., (1996) Actual possibilities. In Principle of Knowledge Representation and Reasoning: Proceedings of the Fifth International Conference (KR'96). Morgan Kaufmann Publishers. Wright, L., (1973). Functions. Philosophical Review 82 (2):139-168. ---(1976). Teleological Explanations: An Etiological Analysis of Goals and Functions. University of California Press.