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way of an entity x is not sufficient to guarantee that x exists as an entity of the
kind Y, nor is the fact that x exists as an entity of the kind Z sufficient to guarantee that it exists also as an entity of the kind Y. As a consequence, a claim
of existence of an entity x is interesting only if it is specified as a claim of
Y-existence, i.e., existence in the mode Y, for a given Y. The ambiguity is
avoided if instead of the generic “do unicorns exist?” we ask “do unicorns
exist as physical entities?”, i.e., “do unicorns have Y-existence?”, where
Y = physical, which according to our current knowledge has a different answer
from “do unicorns have Z-existence?”, where Z = literary.
Furthermore, such a claim is about the Y-existence of x as an object, not
about the meaning of the term “x”, or the concept. As it was put by Quine
(1948, p. 28): “The phrase ‘Evening Star’ names a certain large physical
object of spherical form, which is hurtling through space some scores of millions of miles from here. The phrase ‘Morning Star’ names the same thing, as
was probably first established by some observant Babylonian. But the two
phrases cannot be regarded as having the same meaning; otherwise that
Babylonian could have dispensed with his observations and contented himself
with reflecting on the meanings of his words. The meanings, then, being different from one another, must be other than the named object, which is one
and the same in both cases.” In Gottlob Frege’s terminology (1892), this is
effectively presented by acknowledging that two terms (such as “Evening
Star” and “Morning Star”) can have different senses and nevertheless the
same reference, and also that a term can have Y-sense but no Y-reference, i.e.,
a term can be intended as referring to an entity x of the kind Y even though x
has no Y-existence. Furthermore, this explains the difference between the two
relations Evening Star = Morning Star and Evening Star = Evening Star: the
former required a lot of astronomical ingenuity and knowledge for its discovery, while the latter is a trivial, logical truth, as is any identity x = x, independent of astronomical facts.
It is then worth emphasizing that, as used here, “ontology” is not a synonym of “metaphysics”. Rather, “it refers to the set of ‘things’ a person
believes to exist, or the set of things defined by, or assumed by, some theory.
What’s in your ontology? Do you believe in ghosts? Then ghosts are in your
ontology, along with tables and chairs and songs and vacations, and snow, and
all the rest” (Dennett, 2017: p. 60) (for a wide presentation of a “scientific
perspective” on ontology, see Bunge, 1977, possibly starting from his “list of
ontological principles occurring in scientific research”, p. 16). Of course, at
least some of the things we believe to exist are physical, and some are
psychosocial.
A key problem in ontology—and perhaps the key problem of ontology of
properties—is whether things such as a given mass and mass as such are existing (though possibly abstract) entities, or are just concepts that we produce for
organizing our knowledge. An intermediate position, called extensionalism, is
5 What is measured?
way of an entity x is not sufficient to guarantee that x exists as an entity of the
kind Y, nor is the fact that x exists as an entity of the kind Z sufficient to guarantee that it exists also as an entity of the kind Y. As a consequence, a claim
of existence of an entity x is interesting only if it is specified as a claim of
Y-existence, i.e., existence in the mode Y, for a given Y. The ambiguity is
avoided if instead of the generic “do unicorns exist?” we ask “do unicorns
exist as physical entities?”, i.e., “do unicorns have Y-existence?”, where
Y = physical, which according to our current knowledge has a different answer
from “do unicorns have Z-existence?”, where Z = literary.
Furthermore, such a claim is about the Y-existence of x as an object, not
about the meaning of the term “x”, or the concept
(1948, p. 28): “The phrase ‘Evening Star’ names a certain large physical
object of spherical form, which is hurtling through space some scores of millions of miles from here. The phrase ‘Morning Star’ names the same thing, as
was probably first established by some observant Babylonian. But the two
phrases cannot be regarded as having the same meaning; otherwise that
Babylonian could have dispensed with his observations and contented himself
with reflecting on the meanings of his words. The meanings, then, being different from one another, must be other than the named object, which is one
and the same in both cases.” In Gottlob Frege’s terminology (1892), this is
effectively presented by acknowledging that two terms (such as “Evening
Star” and “Morning Star”) can have different senses and nevertheless the
same reference, and also that a term can have Y-sense but no Y-reference, i.e.,
a term can be intended as referring to an entity x of the kind Y even though x
has no Y-existence. Furthermore, this explains the difference between the two
relations Evening Star = Morning Star and Evening Star = Evening Star: the
former required a lot of astronomical ingenuity and knowledge for its discovery, while the latter is a trivial, logical truth, as is any identity x = x, independent of astronomical facts.
It is then worth emphasizing that, as used here, “ontology” is not a synonym of “metaphysics”. Rather, “it refers to the set of ‘things’ a person
believes to exist, or the set of things defined by, or assumed by, some theory.
What’s in your ontology? Do you believe in ghosts? Then ghosts are in your
ontology, along with tables and chairs and songs and vacations, and snow, and
all the rest” (Dennett, 2017: p. 60) (for a wide presentation of a “scientific
perspective” on ontology, see Bunge, 1977, possibly starting from his “list of
ontological principles occurring in scientific research”, p. 16). Of course, at
least some of the things we believe to exist are physical, and some are
psychosocial.
A key problem in ontology—and perhaps the key problem of ontology of
properties—is whether things such as a given mass and mass as such are existing (though possibly abstract) entities, or are just concepts that we produce for
organizing our knowledge. An intermediate position, called extensionalism, is
5 What is measured?