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Next: 3.1 Newtonian Physics Up: Philosophy of Nature and Previous: 2.6 Objections to Dispositional

3. Problems in Classical Physics

In this chapter, we first discuss the atomic theories of Newton, Descartes and Leibniz to see how they explain dispositional properties. We will see that dispositions (of kinds to be determined) have an unavoidable role in physics, and that mathematical physics is an attempt to relate forms and dispositions in a regular manner. We will see that dispositions are important in almost all kinds of Newtonian physics, in spite of the reluctance of Newton and his contemporaries to acknowledge this fact.

Dispositions first appear in physics as the macroscopic features of observable objects that we wish to explain. The solubility of salt or the hardness of steel (expressed numerically if possible) summarise the results of the experiments that we are considering. Some experimental observations can be explained in terms of the location and configuration of the samples. Almost all phenomena, however, make some reference to dispositional properties, and these cannot be explained purely by the location and shape of these objects, but require causal kinds of ascriptions and analyses, as explained in chapter 2, in terms of causal powers.


Can Physics do Without Causal Powers?

If we wanted, one way to deny causal powers would be to deny the reality of all dispositional properties, as discussed in the previous section, by denying the reality of the subjunctive in the power ascription. On this account, what might happen to objects is completely irrelevant to what really happens. If a glass is never going to be hit, for example, it is purely hypothetical whether it is ever able to break. In physics, as in politics, hypothetical questions need not be answered. They need not be, but they usually are: we would hardly be satisfied with a physical theory, however true, that only holds for laboratory test cases. And if they are answered, on the basis of which real properties are the answers correct, if not dispositional properties?

Another way in which the reality of causes could perhaps be denied is to say that physics is only the discovery of laws that relate events, not the explanation of the properties of things that lead to these events: that is, that physics is (or should be) only concerned with effects, not with causes. It is agreed that all observations are effects of interactions, but it does seem an unnecessarily severe restriction not to permit physicists to speculate on the causal properties of what they are examining, nor to permit them to postulate, for example, potential energy apart from kinetic energy.   Without potential energy, as in a coiled spring, we could not even have the conservation of energy.

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Next: 3.1 Newtonian Physics Up: Philosophy of Nature and Previous: 2.6 Objections to Dispositional
Prof Ian Thompson


Author: I.J. Thompson (except as stated)