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Ernst Mach (1838-1916) is a representative figure of
the early Positivist philosophy of science in physics
at the turn of the twentieth century.
He earned a doctorate in physics from the
University of Vienna in 1860, taught experimental
physics for most of his career at the University of
Prague (1867-1895), and then held the chair of
Inductive Philosophy at the University of Vienna
(1895-1901). He
set himself the philosophical task of implementing the
phenomenalist philosophy of David Hume in physics
while Newtonian mechanics still prevailed in physics,
and he made contributions to physics, psychology, and
education, as well as to philosophy.
Pierre Duhem
(1861-1916), another important early Positivist,
studied physics at the Ecole Normale in Paris, where
he received a doctorate in physics, and was a
professor of physics at the University of Bordeaux for
most of his career.
His principal interest was physical chemistry,
where he aspired to recast the theoretical foundations
of chemical processes on the basis of a generalized
thermodynamics. Unlike
Mach, Duhem accepted the Aristotelian metaphysics,
which he viewed as separate from Positivist physics,
and believed that progress in physical theory
asymptotically approaches a "natural
classification", which he viewed as analogous to
the cosmology of Aristotle.
Duhem’s philosophy differed from Mach’s
philosophy by the former’s acceptance of physical
theory as integral to physics, and his development of
a semantical metatheory to locate theory in Positivist
physics. This
semantical metatheory served as the basis for a
general philosophy of language in the contemporary
Pragmatism, and retrospection reveals that it has been
his more lasting philosophical contribution.
Mach's
Phenomenalism
Prior to the contemporary Pragmatism
philosophers based their philosophies of science on
one or another metaphysical viewpoint.
Though Positivists philosophers including Mach
were explicitly "antimetaphysical" (Mach
even denied that he was a philosopher), they were
actually advocating their own metaphysics while
labeling the views they opposed as
"metaphysical", and using the term as a
pejorative. Positivism
is a philosophy that evolved in reaction against the
various Romantic philosophies, and what the
Positivists meant by "metaphysics" was the
metaphysics of the Romantics.
Just as the views of the Romantics evolved from
the philosophical tradition of the Rationalists,
similarly those of the Positivists evolved from the
tradition of the Empiricists.
Thus Mach's epistemology is very similar to the
views of the Empiricists Berkeley and Hume, and he
explicitly expressed indebtedness to them in his
works.
Mach's
principal work setting forth his phenomenalist
philosophy is his Analysis
of Sensations (1885), which went through five
editions in both German and English, although Mach
also discussed his epistemological views in many of
his other works.
His epistemology postulates
"elements" such as individual sounds,
temperatures, pressures, spaces, times, and colors.
When these elements are considered in relation
to one another, they are studied by the physical
sciences, and when they are considered in relation to
the human mind or rather the nervous system of the
human body, they are called "sensations" and
are studied by psychology. One of the central theses of Mach's Analysis of Sensations is that the only difference between elements
and sensations is the aspect under which they are
viewed, and that physics and psychology therefore have
the same subject matter. The distinction between the physical and the psychical is
entirely a matter of convenience or practicality,
because everything is merely a function of these
elements. Everything
is a mental construct consisting of complexes of
sensations. All
material things including our own bodies and even the
ego are nothing but complexes of elements that have
been constructed by the human mind having some
fixedness or constancy in sense experience.
A fundamental thesis of Mach’s philosophy is
that material bodies do not produce sensations, but
rather complexes of sensations are associated together
by the human mind to produce material bodies.
Ultimately all that is valuable in science is
the discovery of functional relations of dependency of
sensations upon one another.
The constancies that enable our mental
construction of physical bodies have no privileged
reality status. This
is even more so with such mental constructs as the
physicists' molecules and atoms, which are mental
constructs that unlike those of physical bodies are
not found in experience.
The Positivist phenomenalist philosophy is a
nonrealist metaphysics, and if it is generously said
to have an ontology, the ontology consists merely of
the phenomenal elements or sensations.
Mach's
Philosophy of Science
Aim
of Science
Mach’s philosophy of science is rich enough
that it addresses all the four basic topics
conventionally considered in a philosophy of science:
the aim of science, explanation, criticism, and
discovery. He
offers several statements of the aim of science.
One sets forth the "biological task of
science", which is to give the fully developed
human individual with as perfect a means of orienting
himself as possible.
In a second statement he says that the aim of
all science is the representation of facts in thought
either for practical purposes or for removing
intellectual discomfort, since every practical and
intellectual need is satisfied when our thoughts can
represent the facts of the senses completely.
He adds that our knowledge of a phenomenon of
nature is as complete as possible, when thoughts are
set before the mind's eye such that all the relevant
sensible facts can be regarded as a substitute for the
phenomenon itself.
Then the facts appear to be familiar and are
not able to occasion any surprise.
In a third statement he says that the goal of
science is the simplest and most economical abstract
expression of facts.
The noted economy of science involves
uncompleted facts, judgments or laws.
The last two statements of the aim of science
are essentially the same as Mach's theory of
scientific explanation, and do not represent
different aims for science.
And unlike the first, the second and third
statements give an aim that is intrinsic to science.
Scientific
Explanation
Mach set forth his theory of scientific
explanation in many places including his Analysis of Sensations, his "The Economical Nature of Physical
Inquiry" (1882) and "On the Principle of
Comparison in Physics" (1894) reprinted in his Popular
Scientific Lectures (1898).
He says that explanation is the economical
description of experience in terms of elements.
When we examine facts for the first time they
appear confusing.
In time we discover simple stable elements out
of which we can mentally construct the entire factual
domain, and when we have reached the point where
everywhere we can discuss the same facts with other
persons, then we no longer feel lost and the
phenomenon is explained.
The explanation offers a survey of a given
domain of facts with the least expenditure of thought.
The representation of all the facts of a domain
by some one single mental process is economical.
He adds that the greatest perfection in mental
economy occurs when science uses mathematics.
Not all descriptions are explanations; only
direct descriptions can be explanations, while
theories on the other hand are indirect descriptions
and are not explanations. Direct descriptions may be either complete or incomplete.
Description of what is presently observed is a
complete description.
Incomplete description refers to what is
presently unobserved but observable and what is
associated by a law, as for example the movement of a
comet that is presently unobserved or the body of a
man who disappears behind a pillar.
The incomplete description can be completed by
the human mind by means of the associations made by a
scientific law. A
direct description is one in which a single feature of
resemblance among facts is called from memory, while a
theory such as the description of light as a wave
motion is an appeal to another description that had
previously been made elsewhere. A theoretical idea offers more than what we actually observe
in a new fact. It
can be used to extend a fact and enrich it with
features, which we are firstly induced to seek from
its suggestions and, which are often actually found. A theory may lead to discoveries, but the adoption of a
theory always carries a danger: even the most fruitful
theory may be an obstacle to inquiry.
By way of example Mach says the theory that
light is an undifferentiated straight line of
particles impeded the discovery of the periodicity of
light. The
ideal of a given domain of facts is direct
description; such description accomplishes all that
the scientific investigator could wish
Scientific
Criticism
In the Analysis of Sensations Mach states that he has taken Hume as his
starting point, and this starting point is reflected
in his views on scientific criticism.
The scientist like everyone else knows the
elements with complete certainty as sensations.
But scientists and other persons also make
judgments that are laws or generalizations.
Since the aim of science is the adaptation of
thoughts to facts, a new fact may require a new
adaptation, which finds its expression in the
operation of judgment.
A judgment is the supplementing of a
sensational presentation, in order to represent more
completely a sensational fact.
In the adaptation of thoughts to facts the
adaptation can be made only to what is constant in the
facts. Only
the mental construction of constant elements can yield
economy. But our confidence in the constancy in our judgments or
generalizations rests entirely on the supposition,
which in a given case has been substantiated by
numerous trials, that our mental adaptation is
sufficient. And
we must be prepared to find this supposition
contradicted at any moment.
Therefore empirical laws as well as theories
are provisional in Mach's view, but for different
reasons. The
empirical generalizations are provisional, because
they impute constancies to an infinite number of
individual occurrences of sensations while only a
limited number have actually been experienced.
On the other hand theories postulate things
that have never been experienced; no one for example
has ever (in Mach's time) actually seen atoms or
molecules nor has anyone ever experienced Newtonian
absolute space or absolute time.
Mach did not seem to find the provisional
status of empirical laws to be very disturbing and in
fact he considered them to be necessary for science to
have its economy.
But he considered the provisional status of
theories to be an unsatisfactory expediency for
science. His
theory of scientific criticism includes a
phenomenalist criterion that rejects theories.
Initially the Logical Positivists who followed
Mach were reluctant to accept Hume's skeptical views
on scientific criticism, and instead accepted the idea
of "verification", the view the scientific
laws or empirical generalizations can be established
in some permanent sense, an idea that historically had
been definitive of truly scientific knowledge.
But Carnap and the Logical Positivists moved
toward Mach’s acceptance of scientific laws as
provisionally true instead of permanently true, even
as they moved away from his phenomenalism.
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