WHAT IS LOGICAL EMPIRICISM?
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fictions, by means of which scientists can attain summary descriptions
of intricate complexes of sense-impressibns.
Russell, on the basis of a mathematical analysis of these ideas,
developed the view that the imperceptible scientific objects are log–
ical constructions by means of which successful predictions can be
made concerning sense-data. While this theory was accompanied by
a certain metaphysical doctrine of "neutral monism," it was a great
advance over sensationalistic empiricism.
It
replaced the earlier de–
scriptive criterion of empiricism with a more liberal predictive stand–
ard. Predictive criteria of empiricism had been also advanced inde–
pendently by the American pragmatists and by the operationalism
of P. W. Bridgman. In contemporary logical empiricism the principle
is refined to a precision which, while completely excluding meta–
physical terms, does not impose on science the embarrassing con–
straints of strict, sensationalistic empiricism.
Among the terms designating objects, properties and relations
logical empiricism distinguishes two classes:
observation terms
and
non-observation terms.
In the latter are such terms as "atom," "va–
lence," "blood pressure," " the unconscious," "dominance drive," "un–
employment," while among those belonging to the former class are
"potentiometer," "chemical scale," "pressure gauge," "statements
made by a psychoanalytic subject," "words written on a questionnaire,"
"to the left of," "this and this yellow color." Statements in which all
descriptive terms are observation terms form the class of
basis sen–
tences
which is the evidential foundation of scientific knowledge. For
Mach and Pearson the class of observation terms consisted entirely
of terms designating sensations. This restriction was made on the
principle that sensations are immediately apprehended data and so
can serve as the indubitable basis of all empirical confirmation. Even
the Vienna Circle in the first formulations of its methodology re–
garded simple statements asserting the presence or absence of specific
sensations "here-now" as the ultimate, unquestionable basis sentences,
or as they called them, "protocol" sentences. More recently under the
influence of Carnap and Neurath logical empiricists have completely
abandoned the earlier positivistic doctrines of an ultimate basis for
knowledge.
In general, any term which common sense considers as designat–
ing some observable thing or property is admitted into the class of
observation terms. This is entirely in keeping with the practice of
science, in which even the most precise and recondite experiments
are basically dependent on common sense observations, such as:
"This is a glass tube containing a wire filament, etc." Science is there–
by conceived not as a mode of thought radically different from com-
