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I. The Verification Principle
A. J. Ayer, Language, Truth, and Logic:
We say that a sentence is factually significant to
any given person, if and only if, [she or] he knows how to verify the
proposition which it purports to express—that is, if [she or] he knows
what observations would lead [her or] him, under certain conditions, to
accept the proposition as being true, or reject it as being false.
The only meaningful language is either empirically
verifiable or is a mathematical tautology. Rudolf
Carnap's title The Elimination of Metaphysics through Logical Analysis
of Language says it all.
Ludwig Wittgenstein, Tractatus
Logico-Philosophicus:
4.01 A proposition is a picture of reality. A
proposition is a model of reality as we imagine it.
4.02 We can see this from the fact that we
understand the sense of a propositional sign without its having been
explained to us.
4.021 A proposition is a picture of reality: for
if I understand a proposition, I know the situation that it represents.
And I understand the proposition without having had its sense explained
to me.
4.022 A proposition shows its sense. A proposition
shows how things stand if it is true. And it says that they do so
stand.
4.023 A proposition must restrict reality to two
alternatives: yes or no. In order to do that, it must describe reality
completely. A proposition is a description of a state of affairs. Just
as a description of an object describes it by giving its external
properties, so a proposition describes reality by its internal
properties. A proposition constructs a world with the help of a logical
scaffolding, so that one can actually see from the proposition how
everything stands logically if it is true. One can draw inferences from
a false proposition.
4.024 To understand a proposition means to know
what is the case if it is true. (One can understand it, therefore,
without knowing whether it is true.) It is understood by anyone who
understands its constituents.
At the heart of the logical positivists' concerns is
what is commonly called the "observational- theoretical"
distinction. For the positivists, only the empirical observations of the
sciences can said to be actually meaningful; their theories are strictly
speaking "meaningless," though they refer to real objects and
actions, so they have a utility abut them. This is often called an
instrumental view of science.
A variation of this is Carnap's later argument for justificationism.
Granted that a theory can not be verified entirely, we are nonetheless
justified or "confirmed" in holding it to be true based on the
high degree of experimental support.
II. The Falsification Principle
Karl Popper pointed out, however, that the
verification principle itself cannot be verified! Likewise, something
declared probably true always contains the possibility of later disproof.
Instead, he proposed in its place a principle of falsification.
Karl Popper, Conjectures and Refutations:
- It
is easy to obtain confirmations, or verifications, for nearly every
theory- if we look for confirmations.
- Confirmations
should count only if they are the result of risky
predictions; that is to say, if, unenlightened by the theory in
question, we should have expected an event which was incompatible with
the theory - which would
have refuted the theory.
- Every
'good' scientific theory is a prohibition: it forbids certain things
to happen. The more it
forbids, the better it is.
- A
theory which is not refutable by any conceivable event is not
scientific. Irrefutability
is not a virtue of a theory (as people often think), but a vice.
- Every
genuine test of a theory is an attempt to falsify it, or to refute it.
Testability is falsifiability; but there are degrees of
testability: some theories are more testable, more exposed to
refutation, than others; they take, as it were, more risks.
- Confirming
evidence should not count except
when it is the result of a genuine test of the theory; and this
means that it can be presented as a serious but unsuccessful attempt
to falsify the theory…
- Some
genuinely testable theories, when found to be false, are still upheld
by their admirers - for example by introducing ad
hoc in such a way that it escapes refutation.
Such a procedure is always possible, but it rescues the theory
from refutation only at the price of destroying, or at least lowering
its scientific status.
III. Conventionalism
Pierre Duhem has pointed out that what we often call
a "single" theory in science is really built around a network of
auxiliary assumptions. The central theory forms a core which then has a
whole series of assumptions following from it. Given that some conclusion
is derived from a set of premises (e.g. P1. . . . Pn, therefore C), even
if the conclusion is found to be false, it doesn't follow that the central
core is also false since the problem may be at any point along the chain
of premises. In other words, a negative result for a whole theory system need not force a scientist
to reject the central theory but simply to rework the chain of
assumptions. So can any theory in science finally be falsifiable? The
conventionalists would say, no. Theories are adopted not on the basis of
their being true or false but on the basis of their observing well the
conventions of science--simplicity, coherence, ingenuity, subsumptiveness,
reproducibility, etc.
IV. Conceptions of Explanation
- Inferential: scientific explanations are
logical inferences of either an inductive or deductive nature in which
one hopes to provide grounds for believing the conclusions reached.
These conclusions can either be of a universal or a statistical nature
and are testable by experiment or by observation.
- Causal: while they may involve deductive
or inductive arguments and may involve some explanatory claims,
scientific explanations are more about understanding the underlying
causal mechanisms that produce universal or statistical patterns.
- Erotetic: scientific explanations should
be understood as answers to why-questions. This involves contrasting
one class of objects or phenomena with another and offering an
explanation for the relevant differences.
- Compositional: a scientific explanation is
offered based on the properties of various parts of an object.
- Evolutionary: a scientific explanation is
offered by analyzing the development of objects over time, including
objects within a larger system that has been successfully analyzed
from a temporal framework.
- Functional: a scientific explanation is
offered by showing how a complex object or process organizes its
simple component systems.
- Transitional: a scientific explanation is
offered by studying the transitional dynamic an object makes as it
moves from one state to another.
V. Historical Models of Science
-
Cumulative: Scientific
fields develop through adding new knowledge to the accumulation of
past knowledge. Scientific knowledge expands as new insights are added
to the permanent stock of what is known.
-
Evolutionary: Instead of a
simple accumulation, new models replace older ones just as humans
adapt to to their environments. New experimental testing leads to some
results that contradict older ideas, and a survival of the fittest
ideas ensues.
-
Revolutionary: As theories
change so do scientific fields--research programs, methods, goals, and
the surrounding culture of scientific education. Scientific history is
a series of revolutions in understanding and practice. Something like
progress does occur over time, but there is never complete progress
toward an absolute knowledge of the world.
-
Gradualist: Yes, as theories
change so do scientific fields, but these are rarely if ever
revolutions that are incommensurable with previous theories. Rather,
they are small changes in various fields of research that are often
functionally independent, which impact each other over time. When this
occurs, there are justifiable reasons for a field drawing from another
field's models to self-correct its own.
Models of the
Physical Universe
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