Concepts of causal powers

The concept of dispositions has played a key role in the formulation of objective quantum chance in this blog. However, there is ambiguity about what these are as powers. Ruth Porter Groff has helpfully addressed this issue and identified four senses of the term. She identifies dispositional power to be conceptualised as an:

• Activity
• Capacity
• Essence
• Necessitation.

While Groff indicates that there is a further task to work out which is correct in a given context. That is, depending on what is (what the world is like), there could be powers of distinct types. For example, at the various levels of reality (Hartmann) different concepts could play their part. The intention is that clarity on which concept of power applies will strengthen any theory of quantum chance.

These concepts of powers need to be contrasted with what is called the Humean view that there are no necessary connections or causes in nature. That is, there are no powers.

Activity

Consider a film in which each frame is static. Playing the film gives the impression of movement or activity. If activity in the world is like the film, then activity is an illusion or a metaphor. In which case activity is not an aspect of how things are, and the ontology can be called passive. If activity is not just a sequence of static configurations, then activity may not be an illusion. We can follow Groff and use the term anti-passivist to refer to the opinion that activity is a real and irreducible component of the world.

Activity is taken to cover a range of things. Movement, deliberation (moving away from the visual film example), inquiry and chemical reaction (to take an inorganic example). Any instance of causation is an activity.

The view that there is activity in the world has common sense on its side. For example, action as captured by verbs as part of the deep structure of language.

From this perspective, to say that things in the world have causal powers is to say that things engage in activity and are able to do. Reality is in this sense genuinely, irreducibly, non-metaphorically dynamic. In contrast Esfeld's [1] primitive ontology, that is in favour with some who defend the Bohmian version of Quantum Mechanics, is passive and at best kinematic. It is an example of an extreme (or to use Esfeld's own term Super) Humean ontology.

 Real activity contrasts with the Humean view that inanimate matter is essentially passive and never intrinsically active. In real activity the action of things depends on their causal powers. Examples of activity, from Cartwright [2] Hunting causes and using them: Approaches in philosophy and economics, are:

1. The carburettor feeds gasoline and air to a car’s engine ...

2. The pistons suck air in through the chamber...

3. The low-pressure air sucks gasoline out of a nozzle ...

4. The throttle valve allows air to flow through the nozzle ...

5. Pressing the pedal opens the throttle valve more, speeding the airflow and sucking in more gasoline...

6. …

These examples indicate that mechanisms can undertake activity.

Capacity

A capacity is a way that something presently is, such that it could be a way that it presently is not. The phenomenon of a capacity is thus inherently modal, invoking possibility. That is capacity is the potential to be in a possible state for that thing.  This type of potentiality is attached to the nature of a thing and is sometimes called real, or metaphysical possibility, in contrast to logical possibility.

A capacity may be engaged in activity but there is nothing about the concept of a real possibility that requires realism about activity to be either built into it or entailed by it. A power, as a capacity, is a property that need not be fully actualised in the present in order to exist.

Capacities are properties that include, as part of their identity in the present, non-actualized but nevertheless real potential manifestations. By contrast, for the Humean the only properties that exist are categorical properties; properties that are fully occurrent or actual.

Essence

Essentialism is when things (or some kinds of things) are such that they could not be, in part or in full, otherwise without ceasing to be what they are.  Among dispositionalists, Bird [3] defines powers, or potencies, as fundamental properties whose identities are not just dispositional, but fixed. A power as an essence is to be a property whose identity is essential to it.

Necessitation

Necessitation is when one thing is the case, some other thing must be the case. A necessary connection is a power in this sense. Equating powers with necessary connections is proposed by Armstrong [4].

It is not clear that even those anti-passivists who are most focused on defending the reality of necessary connections (in the name of defending the notion of a law) do believe in metaphysical necessitation.

What is meant by the term ‘metaphysical necessitation’? To answer this, we need to know

1. whether one who affirms it believes
1. that things of a given kind necessarily tend to behave in one way or another, or
2. that they must behave in one way or another; and also
2. whether or not one who affirms the existence of metaphysical necessitation holds that given behaviours necessarily bring about assigned outcomes.

Accepting the above would tend someone strongly towards metaphysical determinism and intuitively this would be a natural consequence of necessitation. However, it may be that a version of metaphysical necessity that commits only to the existence of necessary tendencies does not translate into a commitment to what may be called ‘causal necessitarianism,’ or even hard determinism.

Conclusion

It is conceivable that all the concepts described above have role to play in understanding the role of powers in the world. However, from the posts in this blog on quantum physics and in particular quantum chance it is capacity that seems to be the best fit. This is because the potential to have a physical property is attached to a physical object and possibilities are captured by the set of possible values that can be made actual. For example, an electron has the property of spin with the potential to take certain value. The possible values that can be actualised and with whichever probabilities depends on this potential and the context the particle find itself in.

The concept of activity also has causal force but seems better suited to powers of designed mechanism or psychological or social situations. If a theory can be developed of what gives rise to the occurrence of an actual event in Quantum Mechanics, then activity may be a valid concept for the power in question.

Essence plays a role in quantum chance in that the power that governs the tendency for an object, such as an electron, to take particular values of spin is an essential property of an electron. That is, an electron would not be an electron if spin and quantum chance were not aspects of its state.

Necessary connections have a role to play in a physical theory even in the presence of objective chance. The evolution of the wavefunction governed by the Schrödinger equation is deterministic making the state of the object necessarily connected to its state at an earlier time.

However, it is proposed that potentiality and possibility are the key concepts, equivalent to capacity, which play the key role in the developing theory of quantum chance. The most complete treatment to date of powers as potentiality and possibility is by Barbara Vetter [ 5] whose classification of potentiality as a localised modality and possibility as a non-localised modality looks promising. We may then have the quantum state of the electron representing the chance potential to take certain spin values while the possible spin values that can be actualised will depend on the non-localised situation that constrains the quantum state.

 

[1] Esfeld, M., & Deckert, D.-A. (2017). A Minimalist Ontology of the Natural World (1st ed.). Routledge.

[2] Cartwright, N. (2007). Hunting causes and using them: Approaches in philosophy and economics. Cambridge University Press.

[3] Bird, A. (2007). Nature’s metaphysics: Laws and properties. Oxford University Press.

[4] Armstrong, D. M. (2005). Four disputes about properties. Synthese, 144(3), 309-320.

[5] Vetter, B. (2015). Potentiality: From dispositions to modality. Oxford University Press.