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Science & Its Pretenders

Cf. Reading List for core and suggested readings.

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Topics• The Amazing Power of Science – A Very Brie

f Reflection• Science & Pseudoscience – Popper’s Dem

arcation Criterion• Comments on Popper’s Falsificationism• Hypothesis & Evidence• Criteria of Adequacy• Further Example: Evolution vs. Creationism

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The Amazing Power of Science – A Very Brief Reflection

• Influence every aspect of our lives tremendously.

• Change the world with an exceedingly fast pace.

• Produce scientific knowledge with astounding breath and depth.

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Science & Pseudoscience – Popper’s Demarcation Criterion

• About 100 yrs ago, people were deeply interested in theories like:

• Alfred Adler’s (1870-1937) individual psychology:

– An inborn sense of inferiority

– Strive for superiority

– Seemed to be able to explain everything within its field of inquiry!

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• Albert Einstein’s (1879-1955) theory of relativity:

– Relativistic spacetime e.g. simultaneity is relative.

– E = mc2

– One of the two pillars of modern physics.

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• Both claimed to be “scientific”. – “Science” signifies __________,

___________, ___________.

• Yet, Karl Popper (1902-1994) held that theories like Alder’s is actually not scientific.

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• He raised the demarcation problem:

– When should a theory be ranked as scientific?

– Is there a criterion for the scientific status of a theory?

Scientific / Pseudoscientific

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• His criticism of theories like Adler’s:

– Adler’s theory could easily “explain” two “diametrically opposite” cases, e.g.:

• A man pushes a child into the water with the intention of drowning it.

• A man sacrifices his life in an attempt to save the child.

– How?• By appealing to the idea of inferiority

feeling, . . .

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– Its “explanatory power” is just a disguise of its “interpreting power”.

• Points for analysis in your paper, e.g.: How is this interpreting power harmful to a theory? (Hint: meaning shift of some key concepts)

– This apparent strength - capable of explaining everything - is in fact a weakness.

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– Arthur Eddington’s confirmation (1919) of Einstein’s theory was different:• The light-bending prediction• Might be refuted — not always confirmatory!

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• Consequently, Popper proposed:

– The criterion of the scientific status of a theory is its

falsifiability, or refutability, or testability.

• Is this criterion adequate?

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Comments on Popper’s Falsificationism• Two senses of falsifiability:

• Falsifiability as a logical property of statements

– Falsifiable, e.g.:“It never rains on Wednesdays.”“All substances expand when heated.”

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– Unfalsifiable, e.g.:“Luck is possible in sporting speculation.”“There is a ghost in this room which cannot be sensed, directly or indirectly.”

• Falsifiability as a methodological prescription of how scientists should act

– E.g. try to make “all substances expand when heated” unfalsifiable in this sense.

• But both these senses are problematic!

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• 1. The logical sense– Too _______

– Suppose T is a theory having testable predictions.

– Let C be, say, “there is a ghost in this room which cannot be sensed, directly or indirectly”.

– Then T & C has testable predictions and thus scientific in the logical sense!

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• 2. The methodological sense– Too ________

– E.g. the discovery of Neptune• Newton’s theory of gravitation wrongly predi

cted the orbit of Uranus – abandoned it?

• In fact, some scientists tried to rescue Newton’s theory by postulating the existence of an unknown planet.

• Neptune was finally discovered at almost the exact place and time as predicted.

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• The “failure” of Popper's criterion throws up an important question:

– Is it possible to find some common features shared by all the sciences, but not shared by anything else?

– Has science “essential features”?

• Popper assumed that the answer was yes.

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• Ludwig Wittgenstein (1889-1951) argued against essentialism.

– Family resemblance concepts like “game” have no essential features.

– Cf. His Philosophical Investigations, sections 66-7.

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5 -------------- ---------------

GAMESFEATURE

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• The same may be true of “science”.– Note the heterogeneity of science.

• If so, no simple criterion for demarcating science from pseudoscience.

• How actually should we choose among hypotheses – scientific or pseudoscientific?

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Hypothesis & Evidence• The logic of hypothesis testing:

 

Main hypothesis(+ background assumptions)

I1 I2 I3

. . . . .. . . . .

deduction induction

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• Discussion - a daily example:– The problem:

• A lamp does not light up.

– Hypothesis:

– Implication:

– Test:

– Result:

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• Positive evidence does not prove conclusively that a hypothesis is correct.

– There are always competing hypotheses that have the same set of positive evidence.

I1 I2 I3

. . . . .

. . . . .

H

In

I1 I2 I3

. . . . .

. . . . .

H’

In

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• Negative evidence does not prove conclusively that a hypothesis is incorrect.

– A Modus Tollens:

(Hypothesis H • Assumptions A) Implication I

I . (H • A)

– So maybe the trouble comes from A.

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• Example:

– Columbus and the negative evidence against the flat Earth hypothesis

– Supporting the round Earth hypothesis:

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– Saving the flat Earth hypothesis:• Assumption: light travels in curved lines.

• Facts alone cannot decide which hypothesis to accept.– Criteria of Adequacy are needed.

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• Discussion:– What do you think are the criteria of

adequacy?