An unobservable (also called impalpable) is
an entity whose existence, nature, properties,
qualities or relations are not directly observable
by humans. In philosophy of science, typical
examples of "unobservables" are atomic particles,
the force of gravity, causation and beliefs
or desires.However, some philosophers (George
Berkeley for example) also characterize all
objects—trees, tables, other minds, microorganisms,
every thing to which humans ascribe as the
thing causing their perception—as unobservable.
"Unobservables" is a reference similar to
Immanuel Kant's distinction between noumena
(things-in-themselves, i.e., raw things in
their necessarily unknowable state, before
they pass through the formalizing apparatus
of the senses and the mind in order to become
perceived objects) and phenomena (the perceived
object). According to Kant, humans can never
know noumena; all that humans know is the
phenomena. Kant's distinction is similar to
John Locke's distinction between primary and
secondary qualities. Secondary qualities are
what humans perceive such as redness, chirping,
heat, mustiness or sweetness. Primary qualities
would be the actual qualities of the things
themselves which give rise to the secondary
qualities which humans perceive.
The ontological nature and epistemological
issues concerning unobservables is a central
topic in philosophy of science. The notion
that a given unobservable exists is referred
to as scientific realism, in contrast to instrumentalism,
the notion that unobservables such as atoms
are useful models but don't necessarily exist.
W. V. Metcalf distinguishes three kinds of
unobservables. One is the logically unobservable,
which involves a contradiction. An example
would be a length which is both longer and
shorter than a given length. The second is
the practically unobservable, that which we
can conceive of as observable by the known
sense-faculties of man but we are prevented
from observing by practical difficulties.
The third kind is the physically unobservable,
that which can never be observed by any existing
sense-faculties of man.
== See also ==
Empiricism
Logical positivism
Phenomenology
Rationalism
Hidden variable theory
Object of the mind
If a tree falls in a forest
Unobservable chaos
Proxy (statistics), for an unobservable variable
