However, on Markosian’s view, stuff quantification is not an irreducibly different
way of talking about the same things quantified over via a thing quantifier. Rather,
Markosian is explicit that these domains do not even overlap. Mass-quantification is
as fundamental as thing-quantification: on his view, the fundamental language
must include both. Markosian’s (1998, 2004a) primary motivation is to account for
the possibility of objects that lack proper parts but are nonetheless qualitatively
heterogeneous across an extended region of space. On his view, a sphere might
be half red and half blue despite having no parts that are its red half and its blue
half. Markosian explains this apparent possibility by claiming that such an object is
constituted by a portion of stuff that itself contains two portions of stuff, one of which
is red and the other of which is blue. If“portions of stuff”are just things in disguise,
then Markosian’s story is unsuccessful.^58
Recall that one way of formulating the doctrine that there are ways of being is as
the doctrine that there is more than one fundamental quantifier expression. Mixed
ontologies are committed to there being more than one fundamental quantifier
expression, and hence are committed toways of being. On this view, stuff and things
enjoy equally primordial but disparate modes of existing.
2.5.3 Modal Logic I: Necessity and Contingency as Modes of Being
Considermodal logic, the“logic”of possibility and necessity. If modal logic is
properly considered as a part of logic, then“necessarily”and“possibly”are among
the logical vocabulary. On this view, there are logically valid formulae that cannot be
expressed using only the resources offirst-order logic.
Consider now an ontological scheme that consists of necessarily existing abstract
objects and contingently existing concrete objects. On this scheme, existence is
a systematically variably axiomatic feature, since “Everything that exists, exists
contingently”is stateable using only logical vocabulary and is necessarily true when
the quantifier is restricted to one ontological category but necessarily false when
restricted to the other. The hypothesis that contingently existing things and neces-
sarily existing things exist in different ways is especially compelling in this case, since
on this hypothesis that a thing is contingent rather than necessary is grounded in that
thing’s mode of being.^59
Similarly, iftense logicis properly considered as a part of logic, then“it is always
the case”and“it is sometimes the case”are among the logical vocabulary. Presum-
ably, if something is an abstract object, it is necessarily true that it always exists,
(^58) This is the principal complaint of McDaniel (2003). See Markosian (2004a) for a rejoinder. In
McDaniel (2009c), I present my preferred solution to the problem of heterogeneity. 59
See, for example, Vallicella (2002: 23; 2014: 67). One might hold instead that it is grounded in a
difference in essence, but, in chapter 9, I will suggest a way in which essences can be grounded in modes
of being.