Readings about Karl Popper
Transcript of Readings about Karl Popper
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KARL POPPER
LIFE HISTORY
Karl Raimund Popper was born in Vienna, Austria, on 28 July 1902, the son of Simon
Siegmund Carl Popper, a lawyer, and his wife, Jenny Schiff. He turned his inquisitive
and enterprising mind to a variety of activities. He was apprenticed to a cabinet-maker,
joined a youth organisation where he worked with delinquent adolescents, tramped in
the Austrian mountains, taught himself mathematics and physics, and became active
in political movements during the First World War as a socialist. Most significantly, he
studied philosophy at the University of Vienna and was awarded a PhD in 1928. On
11 April 1930 he married Josefine Anna Henninger in Vienna; there were no children
of the marriage. By that time he was an accomplished musician with a decided
preference for classical music and had qualified as a schoolteacher.It was Popper's practical and political interests that first directed him to the
philosophy of science, because he realised that it was vital to be able to tell genuine
knowledge from pseudo-knowledge and superstition. Having become acquainted with
the dominant philosophical school in Vienna, known as the Vienna Circle, he
concluded that its philosophy of science was deficient. It was based on the old
Baconian inductionist theory that science involves making observations and
generalising them into universal laws. This, Popper argued, explained neither how
scientific thought actually proceeds, nor why we consider that its findings correspond
to reality. He therefore formulated a counter-proposal, which he published in 1934
under the title Logik der Forschung; its English translation, The logic of scientific
discovery, was not published until 1959. On Popper's account, science proceeds by
formulating hypotheses. The criterion of a scientific hypothesis is that it generates
predictions that are capable of being falsified by reference to empirical data. These
hypotheses can never be conclusively proved true, so that scientific knowledge is
necessarily provisional. This idea revolutionised the understanding of the nature and
value of scientific knowledge. Albert Einstein read Logikin manuscript and applauded
it vigorously. Popper's radical revision of induction at once brought the philosophy of
science into line with actual practice and provided an unprecedentedly convincing
account of how science succeeds in arriving at knowledge about nature.
With the advance of Nazism in Austria and the growth of anti-Semitism, Popper, who
was of Jewish origin though not a practising Jew, decided to emigrate. In 1936 he
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learnt of an advertisement for a lectureship in philosophy at Canterbury University
College, Christchurch, New Zealand. He applied and took up the position in early 1937.
Despite having acquired a certain level of fame in Europe, Popper was unknown in
New Zealand where knowledge of the significance of his contribution to the philosophy
of science was minimal. As a result, his feelings about Canterbury College were
ambivalent. He was pleased to be safe from the war and from anti-Semitic persecution,
but interpreted the lack of appreciation as hostility to him and his wife, as well as to
what he had to offer. His relations with the head of the Philosophy Department, I. L. G.
Sutherland, were unfriendly and marked by bitter quarrels. He found it hard to accept
that, having made his mark in Europe, he should be inferior in status to a man he
regarded as an academic nonentity. Popper's ignorance of the way British universities
were run made him interpret the inevitable bureaucracy as an attempt to stifle him
personally. And he was probably surprised to find himself in a university where staff
did little research.
Nevertheless, Popper made an immediate impression in Christchurch and became
profoundly influential. He made contact with a number of scientists who were able to
appreciate his contribution to and explanation of their activities. He was specially
befriended at Canterbury by R. S. Allan, the professor of geology, and by H. N. Parton,
a lecturer in chemistry. He was invited by John Eccles, later a Nobel laureate, to
lecture at the University of Otago on the meaning of science and the logic of discovery.
Popper was an enthusiastic and devoted teacher and was widely appreciated by a large
number of students, both at the university and in innumerable lectures he offered in
WEA courses. His lectures were a model of good teaching. He thought aloud and spoke
fluently and slowly, without notes, and never faltered. Ideas seemed to flow from him
in their own inner logical succession. The combination of seriousness and lucidity,
sometimes interrupted by touches of seemingly improvised humour, was completely
persuasive. He spoke with a heavy Austrian accent but was always intelligible. He took
endless care with individual students, on many of whom he left a lasting impression.
The intellectual climate at Canterbury College in those days was decidedly sluggish.
Popper greatly enlivened that atmosphere and in the early 1940s became the most
talked about member of the college staff. He generated among students and colleagues
major debates on the issue of science versus arts and literature. Popper stressed the
importance of scientific research and attacked those die-hard romantics who decried
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science as a threat to humane imagination. He also became well known as an
opponent of communism, which he exposed as a form of totalitarianism at a time
when many people regarded the alliance with the Soviet Union against Germany as a
battle for socialism.
During his years in Christchurch Popper wrote his second major work, The open
society and its enemies, which he considered his contribution to the war effort. It
traced the wish to construct tightly closed social orders, starting with Plato and
working through to Hegel and Marx, whom he held responsible for the triumphs of
both fascism and communism. He also argued that there are no inevitable laws of
historical development, and that the attempt by totalitarian states to suppress
criticism is inevitably self-defeating. Popper's book was published immediately after
the war in London and has since gone through innumerable editions and translations
into many languages. It was a major contribution to modern political and social
thought and continues to be influential. It was taken up with special enthusiasm in
the 1980s and 1990s in eastern European countries wishing to revitalise their
democratic traditions. The frequent misuse ofThe open societyto justify attacks on
the welfare state was never publicly opposed by Popper, although the book made it
quite clear that he saw the democratic state as a necessary protector of weak and
helpless people.
In 1945 Popper was offered a lectureship at the London School of Economics and
Philosophy (LSE) on the strength ofThe open society. He was only too glad to leave
New Zealand. He did, however, contribute to the publication, in 1945, of an important
pamphlet on university reform in New Zealand. Popper turned down an offer of a chair
at the University of Otago and was sounded out about the possibility of a chair in the
University of Vienna; he had no wish to return to Austria. In 1949 he was appointed to
a full professorship at the LSE, where he stayed until his early retirement in 1969.
He continued to lecture and attracted an increasing number of students from abroad.
His relations with many of his most devoted students were now often stormy and, with
the exception of one or two cases, tended to end in open hostility. Popper had become
intolerant of dissent and also inclined to misunderstand the nature of his own
contribution to the philosophy of science. He believed that he had solved the problem
of how scientific knowledge is generated and established. In reality he had merely
moved the problem one step forward and so opened an entirely new problem. In
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demonstrating that all scientific knowledge is only provisional and hypothetical, he
had invited doubts as to the degree to which it genuinely corresponded to reality.
These doubts were pursued by Thomas Kuhn and led him to a relativism which never
gained Poppers approval.
Popper achieved increasing public eminence. He was invited to deliver the William
James lectures at Harvard University in 1950 and took part in many international
conferences and lectures both in the United States and in German and Austrian
universities. He had public debates with Ernst Bloch and Theodor Adorno, two of the
most popular luminaries of Continental philosophy in the 1950s and 1960s, and in
1972 he published his third major book, Objective knowledge, in which he established
a close link between his philosophy of science and the development of neo-Darwinism.
He was knighted in 1965. In 1974 the prestigious Library of Living Philosophers
devoted two volumes to him. Popper formed close personal and intellectual friendships
with many leading scientists. He also visited Australian universities and in 1973 was
awarded an honorary degree by the University of Canterbury during its centenary
celebrations. That year, he held a William Evans fellowship at the University of Otago.
He became a fellow of the British Academy and eventually a fellow of the Royal Society
of London. He was also awarded many international prizes, including the Sonning
Prize in 1973 and the Goethe Medal in 1992, and was esteemed and consulted by
many European statesmen.
Popper continued to think and write until the very last years of his life and delivered
and published two of his most lucid lectures ever at the age of 88 in 1990. He died on
17 September 1994 in Croydon, Surrey; Josefine Popper had died in 1985.
PROBLEM OF INDUCTION
For a brief formulation of the problem of induction we can turn to Born, who writes:
no observation or experiment, however extended, can give more than a finite
number of repetitions; therefore, the statement of a law B depends on A always
transcends experience. Yet this kind of statement is made everywhere and all the time,
and sometimes from scanty material.
In other words, the logical problem of induction arises from (1) Humes discovery (so
well expressed by Born) that it is impossible to justify a law by observation or
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experiment, since it transcends experience; (2) the fact that science proposes and
uses laws everywhere and all the time. (Like Hume, Born is struck by the scanty
material, i.e. the few observed instances upon which the law may be based.) To this
we have to add (3) the principle of empiricism which asserts that in science only
observation and experiment may decide upon the acceptance or rejection of scientific
statements, including laws and theories.
ARGUMENTS AGAINST INDUCTION & SOLUTION TO THE PROBLEM OF INDUCTION
The commonsense problem of induction is based on the bucket theory of the mind
roughly, the assertion that there is nothing in our mind which has not entered
through our senses. But we do haveexpectationsand we strongly believe in
regularities. How can these have arisen? Answer: Through repeatedobservations. The
commonsense view takes for granted that the resulting expectations are justified.
Popper has three thesis:
1. There is no rationally justifiable method of induction2. There is no reliable method of induction.3. Nevertheless, there is a critical methodof science that is rational.
Popper distinguishes Humeslogical problem of inductionwhether we are justified in
reasoning from repeated instancesfrom Humespsychological problem of induction
Why do we have expectations in which we have great confidence? But for Popper, there
is no such thing as induction by repetition (simple enumerative induction), as is
shown by the fact that it is false that "The sun will rise and set once in 24 hours"
(counterexample: the midnight sun at the Earths poles) and "All bread nourishes"
(counterexample: ergotism in a French village). However, this does not show that
simple enumerative induction fails to lead to true, or approximately true,
conclusions most of the time. So, Popper has not even shown that simple enumerative
induction is unreliable, yet alone that there is not reliable method of induction.
Popper rejects Humes assumption (that if there is a reliable method of induction then
it is simple enumerative induction), so he much reformulate the logical problem of
induction:
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L1: Can an explanatory universal theory be justified by assuming the truth of
observation statements?
Note: Talk of explanatory theories alludes to the idea of induction as inference to the
best explanation.
Hypothetico-deductivism is the view that theories are hypothesized under noconstraints. They may arise from a dream or they may arise from inference of
some kind. That is a question of psychology. It that has nothing to do with the
justification of theories, which is based solely on whether what can be deduced
from the theory is true or false.
Here he agrees with the answer Hume would give: NO. To understand the basis of
Poppers claim, consider a very Mills example of a universal theory: "All swans are
white." This theory is not proven by any number of swans that have been observed to
be white because the claim applies to swans that have not been observed.
However, Poppers answer to the following question is YES.
L2: Can the claim that an explanatory universal theory is true or is false be justified by
assuming the truth of observation statements?
For we canprovethat "All swans are white" by observing a black Australian swan.
Modus tollensis the name of a pattern of deductive inference:If T then O
not-O
not-T
This is a deductively valid argument. Let T be a theory, and O be an observational
prediction from the theory, which proves to be false.
There is a logical asymmetry between proof and refutation, which rests only on
deductive logic. There is no need to appeal to the contentious facets of inductive logic
and epistemic probability.
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An affirmative answer to L2is a weaker than an affirmative answer to Humes question.
But it is sufficient to separate us from Russells lunatic who believes he is a poached
egg.
Poppers picture of rational science is one in which competing theories stick theirnecks out, and are subject to severe tests. Some are refuted, but some survive, and
the survivors are rationally justified theories in this weaker sense.
Eliminative induction: If there is a finite list of competing theories T1, T2, , Tn such
that all except one contradicts the known observational statements, then conclude
that the surviving theory is true. This is actually a deductive inference. The weakness
of the argument is the truth of the premise that says that one of the theories in the list
is true.
In other cases, not all theories but one on the list are eliminated. If there is more than
one unrefuted theory, how do we choose between them?
Perhaps we cannot, in which case new tests should be designed in order todecide between (so-called crucial experiments).
An unrefuted theory might be eliminated because it is ad hoc, where adhocexplanations are "explanations which are not independently testable;
independently, that is, of the effect to be explained. A better theory has to
explain what the old theory explained, but "correctsthe old theory, so that it
actually contradicts the old theory; it contains the old theory, but only as an
approximation." (p. 16)
This is connected with Poppers ideas about simplicity, which for Popper comesdoes to falsifiability. An unrefuted theory might be eliminated because it
is complex.
DEMARCATION PROBLEM
The problem of demarcation can be formulated: what distinguishes science from
metaphysics as well as from logic and mathematics?
As opposed to the methodological naturalism of the logical positivists, who treat the
demarcation between science and metaphysics as a difference existing in the nature of
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things, or rather, in the nature of language, Popper is a methodological
conventionalist, proposing rules that embody choices or decisions which are in turn
governed by aims. His demarcation should be judged, Popper maintains, by whether it
proves fruitful in furthering the aims of discovering new ideas and new problems.
DISTINCTION BETWEEN SCIENCE AND PSEUDOSCIENCE
The big difference Popper identifies between science and pseudo-science is a difference
in attitude. While a pseudo-science is set up to look for evidence that supports its
claims, Popper says, a science is set up to challengeits claims and look for evidence
that might prove it false. In other words,pseudo-science seeks confirmations and
science seeks falsifications.
There is a corresponding difference that Popper sees in the form of the claims madeby sciences and pseudo-sciences: Scientific claims are falsifiable that is, they
are claims where you could set out what observable outcomes would be impossible if
the claim were truewhile pseudo-scientific claims fit with any imaginable set
of observable outcomes. What this means is that you could do a test that shows a
scientific claim to be false, but no conceivable test could show a pseudo-scientific
claim to be false. Sciences are testable, pseudo-sciences are not.
So, Popper has this picture of the scientific attitude that involves taking risks:making bold claims, then gathering all the evidence you can think of that might knockthem down. If they stand up to your attempts to falsify them, the claims are still in
play. But, you keep that hard-headed attitude and keep you eyes open for further
evidence that could falsify the claims. If you decide notto watch for such evidence
deciding, in effect, that because the claim hasnt been falsified in however many
attempts youve made to falsify it, it must be trueyouve crossed the line to pseudo-
science.
This sets up the central asymmetry in Poppers picture of what we can know. We canfind evidence to establish with certainty that a claim is false. However, we can never
(owing to the problem of induction) find evidence to establish with certainty that a
claim is true. So the scientist realizes that her best hypotheses and theories are
always tentativesome piece of future evidence could conceivably show them false
while the pseudo-scientist is sure as sure as can be that her theories have been
proven true.
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So, why does this difference between science and pseudo-science matter? As Popper
notes, the difference is not a matter of scientific theories always being true and
pseudo-scientific theories always being false. The important difference seems to be
inwhich approach gives better logical justification for knowledge claims.A
pseudo-science may make youfeellike youve got a good picture of how the world
works, but you could well be wrong about it. If a scientific picture of the world is
wrong, that hard-headed scientific attitude means the chances are good that well find
out were wrong one of those tests of our hypotheses will turn up the data that
falsifies themand switch to a different picture.
CONCEPT OF SCIENTIFIC THEORY
The key feature of Popper's theory exemplified by the modus tolens argument is
"critical testing". In order for critical testing to give valid results, the theory to be
tested must be free from any "looseness"; Popper lists four criteria, or levels of
evaluating, for determining whether a proposed theory is sufficiently "tight" to be
admitted as a "scientific" theory.
We may if we like distinguish four different lines along which the testing of a theory
could be carried out. First there is the logical comparison of the conclusions among
themselves, by which the internal consistency of the system is tested. Secondly, there
is the investigation of the logical form of the theory, with the object of determining
whether it has the character of an empirical or scientific theory, or whether it is, for
example, tautological. Thirdly, there is the comparison with other theories, chiefly
with the aim of determining whether the theory would constitute a scientific advance
should it survive our various tests. And finally, there is the testing of the theory by
way of empirical applications of the conclusions which can be derived from it.(1)
Before looking at these four criteria let us see what Popper means, in general, by a
theory. For Popper, a theoryconsists of a set of statements. Some of these
statements are dependent upon other ones, and some are independent of other
ones. The statements can be classified according to "levels"; one statement is at a
lower level if it can be derived from statements at a higher level. I will call the lower
level statements which depend upon, or can be deduced from, one or more higher level
statementsdependentstatement. Higher level statements have the character of a
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"hypothesis" in relation to dependent statements at a lower level. Statements which
are at the lowest level are called "basic statements", and correspond to specific
singular facts (including "initial conditions") or predictions. Statements which are at
the highest levels (universal statements), are related to the other statements in much
the same manner that axioms are related to theorems in geometry. Statements at
higher levels are said to "explain" dependent lower level statements.
We have two different kinds of statements, both of which are necessary
ingredients of a complete causal explanation. They are (1) universal statements, i.e.
hypotheses of the character of natural laws, and (2) singular statements, which apply
to the specific event in question and which I shall call "initial conditions". It is from
universal statements in conjunction with initial conditions that we deduce the
singular statement, . . . a specific or singular prediction.
The initial conditions describe what is usually called the "cause" of the event in
question. . . . And the prediction describes what is usually called "effect". Both these
terms I shall avoid. . . .(2)
To give a causal explanation of an event means to deduce a statement which
describes it, using as premises of the deduction one or more universal laws, together
with certain singular statements, the initial conditions.(3)
The first criterion Popper requires for a set of statements to be admitted as a theory
is that it must be internally consistent from a formal, logical point of view. In order to
meet this criterion the following conditions must be satisfied. The set of "axiom"
statements must be independent and not contradict one another. Also, there must be
no dependent statements which contradict other dependent statements. Another
condition is that none of these axiom statements may have a "built-in" contradiction
(self-contradictory). When a theory satisfies these conditions, all of the "basic
statements" of the theory can be deduced, in the strictly logical sense, from the axiom
statements. This criterion is necessary to permit "falsification" to extend to higher
level theories. By insuring that this criterion is met, we guarantee that:
If a higher level statement is true, then an immediately lower level, dependent,
statement is true. (Call this "Premise 1")
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We can show what this means by two steps of modus tolens. Suppose we have a
simple theory with one axiom, one "middle level" statement which, for this example, we
will call the "hypothesis", and only one basic statement, the "prediction". Since
Premise 1 is true for this theory, we can show the relationships among the statements
of the theory:
P1. If the axiom is true then the hypothesis is true.
P2. If the hypothesis is true then the prediction is true.
Suppose the prediction turns out false. Then we would say:
P3. The prediction is not true.
Argument 1
If the hypothesis is true then the prediction is true. (P2)
The prediction is not true. (P3)
Therefore, the hypothesis is not true. (modus tolens)
Argument 2
If the axiom is true then the hypothesis is true. (P1)
The hypothesis is not true. (from argument 1)
Therefore, the axiom is not true. (modus tolens)
Because this first criterion was satisfied in this simple theory, a false prediction
"carried through" to prove the axiom of the theory false. If this first criterion had not
been satisfied, this technique of using modus tolens could not have been used, and we
would not know how a false prediction affected the theory as a whole. In more
complex theories, a false prediction might show only that a combination of axioms is
inconsistent in regard to their consequences, but not which of the axioms is the one
which caused the trouble. Because of this, a false prediction may cause the whole
theory to be falsified, or only a part of it.
A theoretical system may be said to be axiomatized if a set of statements, the
axioms, has been formulated which satisfies the following four fundamental
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requirements. (a) the system of axioms must be free from contradiction (whether self-
contradiction or mutual contradiction). This is equivalent to the demand that not
every arbitrarily chosen statement is deducible from it. (b) The system must
be independent, i.e. it must not contain any axiom deducible from the remaining
axioms. (In other words, a statement is to be called an axiom only if it is not deducible
within the rest of the system.) These two conditions concern the axiom system as
such; as regards the relation of the axiom system to the bulk of the theory, the axioms
should be (c) sufficient for the deduction of all statements belonging to the theory
which is to be axiomatized, and (d) necessary, for the same purpose; which means that
they should contain no superfluous assumptions.
In a theory thus axiomatized it is possible to investigate the mutual dependence of
various parts of the system. For example, we may investigate whether a certain part
of the theory is derivable from some part of the axioms. Investigations of this kind . . .
have an important bearing on the problem of falsifiability. They make it clear why the
falsification of a logically deduced statement may sometimes not affect the whole
system but only some part of it, which may then be regarded as falsified.(4)
A second criterion concerns the logical form of the theory. Popper admits only
theories capable of being tested by experience. If the form of a theory is such that its
basic statements simply don't correspond to experience, or are otherwise not testable,then that theory does not qualify as empirical scientific. It may be some other kind of
theory, but it is definitely not to be considered scientific. For a theory to
be scientificit must be testable.
The task of formulating an acceptable definition of the idea of an "empirical
science" is not without its difficulties. Some of these arise from the fact that there
must be many theoretical systems with a logical structure very similar to the one
which, at any particular time, is the accepted system of empirical science. This
situation is sometimes described by saying that there is a great number -- presumably
an infinite number -- of "logically possible worlds". Yet the system called "empirical
science" is intended to represent only one world: the "real world" or the "world of our
experience".
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In order to make this idea a little more precise, we may distinguish three
requirements which our empirical theoretical system will have to satisfy. First, it
must be synthetic, so that it may represent a non-contradictory,
a possible world. Secondly, it must satisfy the criterion of demarcation . . . , i.e. it
must not be metaphysical, but must represent a world of possible experience. Thirdly,
it must be a system distinguished in some way from other such systems as the one
which represents our world of experience.(5)
The third criterion concerns the comparison of one theory with another, and can be
considered a decision process in selecting among theories which satisfy the other
criteria. This is chiefly appropriate when one considers adding a new "axiom" to a
currently accepted theory. Conditions which apply to this criterion include whether
the proposed revision has fewer axioms (Stuart refers to this condition, which has
been known through the ages as Occam's Razor, as "Popper's Chopper"), whether the
proposed revision produces more and different basic statements (predictions), and,
which is particularly significant in selecting from among competing theories, whether
the new axiom produces basic statements (predictions) which contradict basic
statements produced without that new axiom.
The fourth criterion again concerns testability, but of the empirical applications of
the basic statements. If the theory is to be "about reality", its statements must becorrelated with the world of our observations. The few "axiom" statements would
correspond to "laws of nature", and the "basic statements" would correspond to
individual facts or predictions. Acceptance (tentativly) of a theory requires that it be
highly "corroborated" by actual experience.
But how is the system that represents our world of experience to be
distinguished? The answer is: by the fact that it has been submitted to tests, and has
stood up to tests. This means that it is to be distinguished by applying to it that
deductive method which it is my aim to analyze, and to describe.
"Experience", on this view, appears as a distinctive method whereby one theoretical
system may be distinguished from others; so that empirical science seems to be
characterized not only by its logical form but, in addition, by its distinctivemethod.(6)
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Several factors go to make up this criterion. No basic statement (fact or prediction)
may be contradicted by experience. Some basic statements must have been tested
with successful results many times. Not all basic statements must have been tested;
they must simply be capable of being tested. Testability also meant repeatability;
Popper says:
Indeed the scientifically significant physical effect may be defined as that which can be
regularly reproduced by anyone who carries out the appropriate experiment in the way
prescribed.(7)
Additionally, Popper claims we must describe the rules of the method of science.
What he means is a description of the context in which "science" occurs. For example:
Methodological rules are here regarded as conventions. . . . . They might be described
as the rules of the game of empirical science. Two simple examples of methodological
rules may be given. . . . .
(1) The game of science is, in principle, without end. . . . .
(2) Once a hypothesis has been proposed and tested, and has proved its mettle, it
may not be allowed to drop out without "good reason". A "good reason" may be, for
instance: replacement of the hypothesis by another which is better testable; or the
falsification of one of the consequences of the hypothesis.(8)
What happens if this methodology is used in conjunction with Popper's criteria, in
particular, to the body of "scientific" knowledge, as a function of time? At any given
time, there will be the "current (accepted) theory" for that time. As new hypotheses or
"laws of nature" are proposed and tested, some will be, from time to time, refuted or
falsified. Along with the current theory, educators teach some of those theories which
have been "shown to be false". The common view is that as we eliminate falsity, what
we have left is closer to the truth. In other words, along with the current theory, we
have a list of theories or hypotheses which have been discarded, never to be
entertained again.
It is as much of a mistake to think that these "refuted" hypotheses are "false" as it
is to think that the "accepted" theory is "true". Popper himself was aware of this.
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but those who uphold it dogmatically [a system] . . . are adopting the very reverse of
that critical attitude which in my view is the proper one for the scientist. In point of
fact, no conclusive disproof of a theory can ever be produced; [italics mine] . . . If you
insist on strict proof (or strict disproof) in the empirical sciences, you will never benefit
from experience, and never learn from it how wrong you are.(9)
Wherein lies the flaw in our thinking? Different theories may equally account for
the facts. If we were starting out with two theories to compare, our criteria would
provide a means to select between them. What about when a sub-theory, or part of a
theory has been "refuted", and we are considering among alternative sub-theories? In
such a case, the selection is relative to the overarching part of the theory which was
not in question. A single hypothesis could be disconfirmed within a sub-theory, when
a change to the main part of the theory might prevent the disconfirmation!
For example, a long time ago in a far away land, it was believed that Earth was the
center of the universe. That was the accepted theory of the day. With Galileo's theory,
the hypothesis that Earth was the center of the universe was falsified; the Sun held
that distinction. Newton's theory did not disconfirm this, but made it less
tenable. What has happened now that we have relativistic theories? One basic
characteristic of general relativity is that the natural laws of the universe look the
same to all observers, wherever they may be. There is no way to tell that any placeis not the center of the universe! Naturally, that Earth is the center of the universe
is no longer falsified. Of course, neither is it corroborated. So, the hypothesis that
Earth is the center of the universe was held to be true in early science, "falsified" in
later science, and is now no longer falsified. (Of course, this view is not held by many
either.) As a practical matter, Earth is chosen as the center of the spatial coordinate
system for many purposes.
In addition to this theoretical consideration, there is the matter of what Popper
calls "inter-subjectivity". Inter-subjectivity operates at the level of our holding up
some material object and agreeing to call it a "stone". Such inter-subjectivity provides
room for tacit and concealed assumptions about what the nature of the world is
like. In many cases, the progress of science has required rethinking the most simple
and thoroughly accepted so-called "basic facts". *
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Any significant revision of the expression of any of these "basic facts" will change
the primary facts to be accounted for by a theory. Such a change in basic facts could
result in a previously disconfirmed hypothesis becoming, under the revised theory, not
disconfirmed. So "falsity" seems to be no more "find-outable" than "truth".
CONCEPT OF FALSIFICATION
(WHEN IS A THEORY FALSIFIED?)
Falsifiability or refutability is the logical possibility that an assertion could be shown
false by a particular observation or physical experiment. That something is "falsifiable"
does not mean it is false; rather, it means that ifthe statement were false, then its
falsehood could be demonstrated.
The claim "No human lives forever" is not falsifiable since it does not seem possible to
prove wrong. In theory, one would have to observe a human living foreverto falsify
that claim. On the other hand, "All humans live forever" is falsifiable since the
presentation of just one dead human could prove the statement wrong (excluding
metaphysical assertions about souls, which are not falsifiable). Moreover, a claim may
be true and still be falsifiable; if "All humans live forever" were true, we would never
actually find a dead human, and yet that claim would still be falsifiable because we
can at least imaginethe observation that would prove it wrong.
Some statements are only falsifiable in theory, while others are even falsifiable in
practice (i.e. testable). For example, "it will be raining here in one billion years" is
theoretically falsifiable, but not practically so.
WHEN IS A THEORY BECOMES SCIENTIFIC?
Falsifiability, particularly testability, is an important concept in science and
the philosophy of science. The concept was made popular byKarl Popper in his
philosophical analysis of the scientific method. Popper concluded that
a hypothesis, proposition, or theoryis "scientific" only if it is, among other things,
falsifiable. That is, falsifiability is a necessary (but not sufficient) criterion for scientific
ideas. Popper asserted that unfalsifiable statements are non-scientific, although not
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without relevance. For example, meta-physical or religious propositions have cultural
or spiritual meaning, and the ancient metaphysical and unfalsifiable idea of the
existence of atoms has led to corresponding falsifiable modern theories. A falsifiable
theory that has withstood severe scientific testing is said to be corroborated by past
experience, though in Popper's view this is not equivalent with confirmation and does
not guarantee that the theory is true or even partially true.
Popper invented the notion of metaphysical research programs to name such ideas. In
contrast to positivism, which held that statements are senseless if they cannot be
verified or falsified, Popper claimed that falsifiability is merely a special case of the
more general notion of criticizability. Still, he admitted that tests and refutation is one
of the most effective methods by which theories can be criticized.
PROGRESS OF KNOWLEDGE
Popper's view differs from the positivists in that he thinks that what he describes is a
theory of scientific growth and change over history. Recall that the positivists were
rather indifferent to the question of whether their model of scientific knowledge
resembled real, historical science because they saw their task as normative; they were
describing an ideal of how a "rational" science ought to be, even while admitting that
actual human science was often less. Unlike the positivists Popper makes no claim to
describe an idealized perfected or "rationally reconstructed" science; what he claims to
describe is real historical science. The story of the growth of knowledge, he thinks, is
the story of putting forward "bold,"or "risky"conjectures, and then testing them by
making empirical predictions from them, until they are refuted. Then
a new hypothesis is conjectured (often a modification of the old refuted one) and the
testing begins all over again. The growth of knowledge is not a matter of "construction"
upon a firm foundation (as depicted in the "pyramid model") but of "criticism" of
speculative, but testable, conjectures. New hypotheses come from criticisms made
of discarded old hypotheses rather than the accumulation of empirical data.
Thus Popper speaks of the progress of knowledge as "criticism and the growth of
knowledge" which is a process of "conjectures and refutations." Inevitably every
conjecture ultimately meets its nemesis in some fact with which it cannot deal. It is
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then considered "refuted" and is replaced with a better conjecture, where "better" here
of course cannot mean more "confirmed" or supported by the evidence, but it means
more testable.
Good theories, according to Popper, must be testable, but "testable" means
potentially falsifiable, refutable. Therefore, in proposing theories, the more refutable,
(i.e. the more "testable"), the better. Popper expresses this point by saying that
"conjectures" must be "risky" or "bold." Of course it would do little to advance the
growth of knowledge repeatedly to propose totally off-the-wall "risky" conjectures just
to shoot them down. The occasions when science advances most are whenattempts to
refute risky conjectures fail, thus corroborating bold guesses, or occasions when safe
"modest" conjectures relying mostly on accepted beliefs are, surprisingly, refuted, thus
falsifying "established" wisdom.
As a consequence, over time, the progress of knowledge demands that theories
become more and more testable, and hence more and more "risky." It follows that
the rational scientist never defends any theory to be established "beyond refutation."
Since the more precise and the more comprehensive a hypothesis is, the greater the
"risk" it takes of being refuted, the historical direction of science will be towards ever
more precise theories, comprehendingever greater domains of phenomena.
For these reasons, the Popperian can never believe it is rational to hold any theory tobe true; to do so would be "irrational" because it would bring the critical process by
which knowledge grows to a halt. Inasmuch as one can never know that the "last
possible test" has been devised, Popper holds that any theory can, and ought to,
be tested until it is ultimately shown to be false. No rational inquirer ever holds his
theory to be true, nevertheless Popper holds his doctrine is realistic in that the
process of criticism and the growth of knowledge is in effect a method of filtering out
the false, thus narrowing the bounds within which truth can be found, even though it
can never be known to be in fact found. Thus as knowledge grows we do indeed learn
more and more about the nature of reality; it is the nature of reality which "selects"
those theory's which in effect survive best the scientists' onslaught of tests.
PROGRESS OF SCIENCE
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Science is guesswork, doxarather than episteme. In place of the old ideal (or rather
idol) of science as the search for absolutely certain, demonstrable knowledge, Popper
argues that the demand for scientific objectivity makes it inevitable that every
scientific statement must remain tentative for ever. Verification of scientific
knowledge is replaced by falsification. Accumulation of irrefutable facts is replaced by
conjecture and refutation.
Poppers view of science as conjectural challenges the idea that the empirical base
of science is an unchangeable and stable foundation from which we can measure
progress. As he says:
The empirical basis of objective science has thus nothing absolute about it. Science
does not rest upon solid bedrock. The bold structure of its theories rises, as it were,above a swamp. It is like a building erected on piles. The piles are driven down from
above into the swamp, but not down to any natural or given base; and if we stop
driving the piles deeper, it is not because we have reached firm ground. We simply
stop when we are satisfied that the piles are firm enough to carry the structure, at
least for the time being.
Strictly speaking, the truth value of any scientific theory must be regarded as false. If
it has been falsified, it is false; if not, then it will at some future point be demonstrated
false. A theory is corroborated if it has withstood genuine attempts at falsification, but
it is never anything more than a working hypothesis, never demonstrated true. This is
born out according to the logical asymmetry between verification and
falsification. While it is impossible to verify a universal law by reference to some
putative confirming experience, a single counter-instance to the universal law
conclusively refutes it. We pursue truth, but at best, we can only have the expectation
of finding our where our theories are mistaken and replacing them with better ones.
A good scientific theory, for Popper, is one that puts itself at a genuine risk of being
proved false due to its high informative content. This has a rather paradoxical result
especially if we are inclined to think that the more probable a theory, the better it
is. For Popper, we should not assume uncritically that high probability is an aim of
science. The more improbable a theory, the better it is as a scientific theory because
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probability and informative content vary inversely. The higher the informative content
of a theory, the lower the probability the theory will have. This will be clear since the
higher informative content means that scientists will have a better chance of
demonstrating that the theory can be falsified. The aim of science then is not high
probability of theory turning out to be true, but rather high informative content
leading to the demonstration of its falsehood.
Still this may appear insufficient to describe the progress of science. Does
knowing what is false give us progress? Popper seems to have recognized this
point. He writes:
this picture of science--as a procedure whose rationality consists in the fact that we
learn from our mistakes--is not quite good enough. It may still suggest that scienceprogresses from theory to theory and that it consists of a sequence of better and better
deductive systems. Yet what I really wish to suggest is that science should be
visualized as progressing from problems to problemsto problems of ever increasing
depth.
Popper viewed problem-solving as the hallmark of science but to account for a
sequence of better and better deductive systems, he required an idea of truth. He
argued that the very idea of truth allows us to recognize mistakes and engage in the
rational pursuit of eliminating mistakes. The standard of an objective truth about the
world, of which our empirical testing gives results, is the basis for the very idea of
error. What is needed for progress, however, is some explanation of how the
succession of false theories constitutes progress. The answer came in part with
Poppers attempt at the theory of verisimilitude--that later theories have a higher
degree of verisimilitude or truth-likeness because though all are false, they get
progressively closer to the truth. That is, the truth-content is higher and the falsity-
content is lower as we move from earlier to later theories. In spite of the fact that
Poppers formal definitions of verisimilitude were demonstrated to be problematic, he
maintained that the common sense notion that science aims at truth in the sense of
correspondence to the facts or to reality remained a valuable heuristic device. A well-
corroborated successor to a falsified theory is a better approximation to truth provided
that it has also met some new predicative success.
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So, for Popper, scientific progress is understood in terms of how theories replace
others via the severely critical process of falsification. A theory that has replaced a
predecessor has a higher degree of testability and universality, richer content, greater
precision and predicative power and deals with problems of ever-increasing depth that
result in more satisfactory explanations. Moreover, the idea of progress from theory to
theory requires increasing fertility in that new conjectures will provide guidance in
research to further problems and solutions.
As Popper generalized his falsification theory to apply more broadly to problem
solving in other areas of non-scientific inquiry, he extended his critical rationalism
such that progress in metaphysics, politics and morality is achieved by the degree to
which a discipline engages in rational discourse in advancing and criticizing
theories. The new criterion of demarcation is not between science and non-science,
but rather between systems devoid of rational value and systems that are engaged in
solving serious and interesting problems. The boundary between science and
metaphysics, or science and politics remains sharply drawn on the basis of
falsifiability, but this does not mean metaphysics or politics is meaningless discourse
as long as ideas are subjected to rigorous criticism and stand only as tentative and
fallible solutions to problems. Popper even recognizes that metaphysics is an
inevitable precursor to science, as a sort of embryo in the development of scientific
hypotheses. The main obstacle to progress in these disciplines is not that they fail to
be scientific but rather that they embrace dogma, i.e., ideological intolerance or simply
become subject to intellectual fashion.
CONCEPT OF TRUTH
Popper viewed problem-solving as the hallmark of science but to account for a
sequence of better and better deductive systems, he required an idea of truth. He
argued that the very idea of truth allows us to recognize mistakes and engage in therational pursuit of eliminating mistakes. The standard of an objective truth about the
world, of which our empirical testing gives results, is the basis for the very idea of
error. What is needed for progress, however, is some explanation of how the
succession of false theories constitutes progress. The answer came in part with
Poppers attempt at the theory of verisimilitude--that later theories have a higher
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degree of verisimilitude or truth-likeness because though all are false, they get
progressively closer to the truth. That is, the truth-content is higher and the falsity-
content is lower as we move from earlier to later theories. In spite of the fact that
Poppers formal definitions of verisimilitude were demonstrated to be problematic, he
maintained that the common sense notion that science aims at truth in the sense of
correspondence to the facts or to reality remained a valuable heuristic device. A well-
corroborated successor to a falsified theory is a better approximation to truth provided
that it has also met some new predicative success.
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science-and-pseudo-science/
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