4.4 Dispositions in nature
This dispositional essentialism leaves two important questions still unanswered.
The first question is whether all, or only some of an object’s
properties are dispositional. We would naively think that structural properties
such as shapes, sizes and arrangements of parts are not dispositional properties,
but Bird (2005b) argues that we cannot be sure of
this. It would be useful to have a clear understanding of how (or whether) dispositional
and non-dispositional properties can be simultaneously instantiated in an object.
The second question concerns ontology: what is the relation between dispositional
properties and the being (or substance) of the object with such properties?
Menzies (2009) doubts, for example, that properties
can be correctly construed as causal powers. Surely, he says, it is objects
rather than properties which are the correct bearers of enduring causal powers.
In the previous section, we saw how science analyzes and constitutes dispositional
properties and how those properties are explained as forms of some essential more-fundamental
dispositions or propensities. We can now philosophically generalize that analysis
in order to formulate a new view of the constitution of objects, such that dispositional
essentialism logically follows. This new constitution is to take powers or propensities
themselves as the persisting ‘stuff’ of which objects are made. That is, I argue
that we should identify ‘propensity’ and ‘substance’ so that natural objects, as
‘forms of propensity’, are then ‘forms of a substance’ in nearly the manner of Aristotle.
It is admittedly a large metaphysical leap to identify propensity as substance,
but I will argue that the identification is grammatically correct, philosophically
sound, historically defensible, and physically correct, and that it even helps clarify
interpretations of quantum physics. It furthermore agrees with the Eleatic Principle:
that existence should only be given to that which has causal power. In a more modern
age, this would be called a ‘pragmatic’ view of substance, as attributing significance
not to what something merely is but to what it can do. The identity
of substance and propensity is claimed in the same sense that, while the morning
star and the evening star are initially known independently, they turn out to refer
to the same (ontological) being. This identification should be the next development
for those who adhere today to dispositional essentialism. Instead of worrying about
‘ungrounded dispositions’, we will see that dispositions are able themselves to
be grounds or bearers of properties.