Active and passive properties

This post was inspired by a talk Barbara Vetter gave to the Ockham society last night. The view of dispositions as not necessarily needing a stimulus is hers – the extra stuff I’ve added shouldn’t be blamed on her!

Folklore has it that dispositions are individuated both by their stimulus conditions and their manifestations. Fragility, for example, is said to be roughly the disposition to break when struck. There is an active element (breaking) and a passive element (being struck) in this characterization. But could we have purely active or purely passive dispositions?

Consider the purely active case first. This would be a disposition to behave a certain way, independently of external stimuli. There’s one particularly clear candidate; radioactivity. An atom is radioactive if it is disposed to decay spontaneously.

Purely passive cases are harder. But maybe edibility is an example. What matters to whether something is edible is whether or not some external entity can come along and eat it; what happens next (the manifestation) seems to be somewhat irrelevant. Of course, in some sense of ‘edibility’, being edible requires not poisoning the eater when eaten. But leave these cases aside. Or perhaps something like ‘strikability’ is a better example.

If these cases are as I’ve described them, then a kind of pattern emerges. There are similar kinds of property which may be characterized by an active condition (manifestation), by a passive condition (stimulus), or by both, as follows:

Property Passive condition Active condition
Breakability Unspecified Breaking
Fragility (?) Striking Breaking
Strikability Striking Unspecified

A question which now arises is – which of these kinds of properties count as dispositional? I suggest they all do, even though we don’t normally think of properties like ‘strikability’ when giving examples of dispositions. Perhaps this is partly because strikability, if it is a disposition, will be an extrinsic disposition.

The question mark after fragility is because I’m not sure that fragility really is the disposition to break when struck – perhaps it’s just the disposition to break, or the property of breaking easily (this is actually how the OED defines it.) Evidence for this claim might be that ‘fragile’ and ‘breakable’ are used pretty much interchangeably on packaging.

Provisional conclusions –

  • Some dispositions lack a (non-trivial) stimulus condition (radioactivity is a clear example).
  • We can perhaps make sense of properties which lack a (non-trivial) manifestation condition (edibility and strikability are not-so-clear examples).
  • We can lay out a spectrum of possible properties ranging from ‘purely active’ to ‘purely passive’, depending on the role of active and passive conditions in characterizing those properties.
  • Which properties count as dispositional is an interesting and non-trivial question.
Active and passive properties