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Scientific Realism’s Ontological Commitments
Like all versions of realism, scientific realism is at heart a thesis about the sort of things that
populate our universe. The realist’s semantic commitments set the foundation for her
ontological view. Consider, again, the sentence
Electrons have negative charge
. The sentence
contains two theoretical terms: “electron” and “negative charge.” A realist will likely defend
the thesis that “electron” refers to an ontological robust entity and that “negative charge”
refers to an ontologically robust property. However, suppose that the sentence
Electrons have
negative charge
is not a description. This sentence will only fail to be a description if at least
one of the two theoretical terms is not in the business of referring. If “electron” has no
semantic content but is, instead, merely a useful syntactic placeholder, then it makes no sense
to ask about the nature of electrons. This would be analogous to asking about the nature of a
syntactic placeholder that I artificially introduced into this chapter to drive up the word count:
zzzYYYzzz. Were you to ask your friend “What kind of a thing is zzzYYYzzz?” she would
give you a funny look. “zzzYYYzzz” is not in the business of referring; wondering what a
zzzYYYzzz is like betrays a important conceptual confusion. The same goes for the
theoretical terms of science. If scientific claims are not descriptions, it makes no sense to ask
about the nature of scientific entities. If descriptivism is false, wondering about the
ontological status of scientific entities betrays a conceptual confusion about the role of
scientific terms. By hypothesis, there are no such things.
Once the realist has accepted a descriptivist account of scientific language, she is free
to think that scientific theories accurately describe the world. The scientific realist is
committed to the
approximate truth
of (some) scientific theories. The realist is, of course, not
committed to the truth of all contemporary theories. It is deeply implausible to suppose that
all of our contemporary theories are accurate. Rather, the scientific realist is only committed
to the truth of our
best
scientific theories. Furthermore, the realist is not committed to the
truth,
simpliciter
, of any scientific theory. It is implausible to suppose that any contemporary
theory is entirely true. The realist is only committed to thinking that some of our best
scientific theories get things mostly right. Thus, the scientific realist is committed to the
approximate truth of some of our best theories.
Commitment to the truth of scientific theories is not, however, all there is to the
realist’s ontological commitments. We can ask the following question: What is the
ontological status of the theoretical entities of science? This question can be helpfully
rephrased: In virtue of what are sentences containing terms that refer to theoretical entities (in
non-opaque contexts) true? Broadly speaking, philosophers who answer this question fall into
two camps: constructivist and realist. How one answers this question will determine what one
thinks about the ontological status of the theoretical entities of the sciences: are they
ontologically robust or merely human constructs?
The constructivist holds that (some) sentences containing theoretical terms are true in
virtue of human mental states. Consider, by way of example, a very coarse-grained
description of Kuhnian constructivism: the sentence
Electrons have negative charge
is made
true by the scientific community’s acceptance of a certain paradigm. Were the contemporary
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