Readings about Karl Popper

7/30/2019 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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19/22

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


20/22

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


22/22

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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http://blogs.scientificamerican.com/doing-good-science/2011/10/04/drawing-the-line-between-

science-and-pseudo-science/

http://www.xenodochy.org/article/popper.html

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http://www.loyno.edu/~folse/Popper.html

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Documents

Readings about Karl Popper