I’ve been lucky enough to have a world-class conference on my doorstep over the last three days – Anna Marmodoro organized everything really well, and it was great to hear Alexander Bird, Kit Fine, EJ Lowe, Stephen Mumford, Ernest Sosa and others in full flow. Over the next week or so I’ll be discussing a few of the suggestions raised there in this blog. Let’s begin with natural necessity.
On Tuesday afternoon, Markus Schrenk and Stephen Mumford gave two parts of a very interesting ‘Nottingham paper’ on the relation between power and necessary connection. The written version of Markus’ paper is here. Very briefly, they argued that necessary connections between (token local) events should be carefully distinguished from powers, and that we should believe in the latter but not the former.
The master argument is based on the idea that any causal chain can be interfered with, so no episode of singular causation or disposition-manifestation occurs with natural necessity. The way the conclusion was stated was that they were denying natural necessity, although rescuing powers, causation, natural possibility, forces, tendencies, and so on.
What does their denial of natural necessity amount to? Their target notion of necessary connection is a relation between events – so it looks like all it takes for there to be no naturally necessary connections in the world is that for each actual transition from cause to effect or from disposition to manifestation, that transition could have (naturally) possibly not occurred. A token cause, considered by itself, does not necessitate any particular effect, since the intrinsic specification of the cause does not exclude the possibility of interfering environmental factors. This claim seems plausible – so maybe there is indeed no natural necessity to the relation between local token events. This, I think, is interpreted as a partial vindication of the Humean denial of necessary connections.
A different candidate sort of natural necessity is the conservation of charge. In conversation afterwards, Mumford suggested that he wanted to take this form of necessity as a Kripkean metaphysical necessity. The idea would be that electromagnetic interactions form a natural kind, and that it is part of the constitution of this kind that all such interactions conserve charge. So although there is metaphysical necessity in the picture, we still haven’t found any non-trivial natural necessity (unless, of course, we follow Bird and Edgington in identifying natural necessity and metaphysical necessity).
However, natural necessity does re-enter the picture when we look beyond particular pairs of localised events, at the bigger picture. Consider ‘maximally conditional’ natural necessity – specify a past light cone, and the effect follows with necessity if the underlying physics is deterministic. If the underlying physics is indeterministic, instead we get probabilities for effects following with necessity. Either way, there is at least one non-trivial form of natural necessity. This point was raised a few times in discussion, by Jennifer McKitrick and then by John Heil and Galen Strawson. Mumford’s reply, which seemed to appeal to Anscombe’s heterodox view of determinism, wasn’t enough to leave me satisfied.
So although Schrenk’s and Mumford’s rejection of necessary connections between token local events is plausible, and their distinction between necessary connections and powers is attractive, I think the dispositional essentialist should resist their headline claim that natural necessity is non-existent.