This is a previous article of mine, published in the book: M. Suárez (ed.), Probabilities, Causes, and Propensities in Physics, Synthese Library, Springer, 2011. [pdf]
Recently, the much philosophical work has emphasized the importance of dispositions for realistic analyses of causal processes in both physics and psychology. This is partly because of the attractiveness of the thesis of dispositional essentialism, which holds that all existing things have irreducible causal powers, and such views are advocated by [many philosophers]. The thesis opposes the views of Ryle  who sees dispositions as merely `inference tickets' or `promises', and Armstrong  who sees them as derived from universal laws combined with nondispositional properties. Mumford  articulates a common aspect of dispositional essentialism, to imagine how the concept of universal laws could be rather replaced by talk of specific objects and their dispositions.
It may well be that concepts of more sophisticated kinds of dispositions allow us to make headway in understanding the above complications within the framework of dispositional essentialism. I therefore continue the analysis of kinds of dispositions, to consider the possibility of derivative dispositions, and later consider whether these together may form a structure of multiple generative levels. This paper therefore consists of proposals for what those concepts might mean, and of analyses of examples in physics and psychology that appear to need such concepts for their understanding. We need to distinguish the cases whereby new dispositions come about from rearrangement of parts, from possible cases where they are `derived' or `generated' in some more original way.
2 Beyond simple dispositions
2.1 Changing dispositions
Most examples of dispositions in philosophical discussions are those, like fragility, solubility, radioactive instability, whose effects (if manifested) are events. If a glass exercises its fragility, it breaks. If salt shows its solubility, it dissolves, and the manifestation of radioactive instability would be a decay event detected say with a geiger counter. However, physicists want to know not merely that these eventsoccur, but also how the dispositions themselves may change after the manifestation event. In the cases here, the fragility of the parts or the stability of the nuclei may change as results of the manifestation events, and it is still part of physics to describe the new (changed) dispositions as accurately as possible. Such descriptions are part of dynamical accounts, as distinct from descriptive accounts events.
Sometimes, new dispositions may be ascribable after an event which could not be done so before an event. The fragments of a broken glass may be able to refract light in a way that the intact glass could not, for example. The dissolved salt may be to pass through a membrane, in contrast to the dispositions of the initial salt crystals. The fragments of nuclear decay may possibly decay by emitting electrons in a way the parent nucleus could not.
In general, it appears often that new dispositions may be truthfully ascribed as the result of the operation of a prior disposition. If the ascription of dispositions is attributed to the existence properties of some object, then it appears that, in the above examples, new dispositions come into existence as the manifestation of previous dispositions. Since now one disposition leads to another, some philosophical analysis is called for.
2.2 Rearrangement dispositions
The existence of some of these new dispositions may perhaps be successfully explained as the rearrangement of the internal structures of the objects under discussion, which are then presumably composite objects. The refraction by pieces of broken glass, in contrast to the original smooth glass, has obvious explanations in terms of the shapes of the new fragments. Salt's diffusion through a membrane, once dissolved, is presumably because of the greater mobility of salt ions in solution compared with the crystal form.
Science is largely successful in explaining such dynamical evolutions of empirical dispositions of natural objects. It bases the explanations in terms of changes in their structural shapes and arrangements of their parts, along with the fixed underlying dispositions or propensities of these parts. It is from the dispositions of these parts that, according the structure, all their observed dispositions and causal properties may be explained.
The existence of new dispositions by rearrangement of the parts of an object, I take to be non-controversial within existing philosophical frameworks. It appears that typical philosophical analyses need only slight modifications to take into account the way the derivative dispositions of an aggregate are explained in terms of recombinations of the dispositions of its parts.
2.3 Derivative dispositionsHowever, it also appears that not all dynamical changes of dispositions occur by rearrangements of parts, and these are what in this paper I want to call derivative dispositions. There are some cases, to be listed below, where new dispositions come into existence, without there being any visible parts whose rearrangement could explain the changes. The next section gives some examples of what appear to be such derivative dispositions, and this is followed by a more general analysis of how these might work.
If there turns out to be a sequence of derivative dispositions, then the combined structure may be said to be that of `multiple generative levels'. We will see some examples below.
3 Examples of derivative dispositions
If we look at physics, and at what physics regards as part of its central understanding, one extremely important idea is energy. Physics talks about kinetic energy as energy to do with motion, and potential energy as to do with what would happen if the circumstances were right. More specifically, if we look at definitions of force and energy which are commonly used to introduce these concepts, we find definitions like
3.1 Energy and Force
- force: the tendency F to accelerate a mass m with acceleration F/m.
- energy: the capacity E to do work, which is the action of a force F over a distance d,
- potential energy field: the field potential V(x) to exert a force F = -dV/dx if a test particle is present.
- potential energy field: the disposition to generate a force, and
- force: the disposition to accelerate a mass, and
- acceleration: the final result.
Admittedly, many physicists and philosophers often manifest here a tendency to say that only potential energy is `real', or conversely perhaps that `only forces are real', or even that `only motion is real', and that in each case the other physical quantities are only `calculational devices' for predicting whichever is declared to be real. Please for a while apply a contrary tendency to resist this conclusion, at least to the end of the paper. In §5 I will be explicitly evaluating such `reductionist strategies, along with the comparative roles of mathematical laws and dispositional properties within a possible dispositional essentialism.