Unit 2 The logic of scienti fi c

discovery

Demarcation

Science and knowledge?

• What is the difference between science and pseudo-science?

• Scientists claim to increase our knowledge of the world

• But don’t astronomers and protagonists of intelligent design claim the same?

demarcation

• What kind of theory, what kind of methodology, is useful and will advance humankind.

• This is called the demarcation problem.

Back to epistemology• Two main ideas about how to increase

knowledge: empiricism and rationalism. • Two related modern positions: – logical positivism – critical rationalism

Logical Positivism

Positivism

• positivism was developed by the 19th century philosopher and sociologist August Comte.

• Positivism is an epistemological perspective that holds that sense experience and positive verification are the only ways to get to authentic knowledge.

Vienna circle and logical positivism

Ludwig Wittgenstein (1889-1951)Tractatus Logico-Philosophicus

Whereof one cannot speak, thereof one must be silent.

Analytic-synthetic (again)

• Synthetic: All men are arrogant• Analytic: All men are human• Analytic sentences and claims are empty, they

are tautological• Therefore only synthetic claims (induction) are

scientific

Sensory experience

Protocol sentences Theory

reductionism

• Every meaningful statement can be reduced to protocol sentences

• Protocol sentence: a sentence that describes immediate experience

Confirmation and structure

• According to the verifiability principle a proposition is only "cognitively meaningful" if there is a procedure to determine whether it is true or false.

• The logical positivist tried to find logical patterns in experience, unobservable structures, laws, like the law of gravity.

Logical positivism in short

• The analytic-synthetic distinction• The verifiability theory of meaning

The problem of induction

We can verify (confirm) anything with everything

• Hypothesis (h): All ravens (F’s) are black (G)• Every f we see that is g confirms h• All F’s are G is logically equivalent to all

nonblack things are not ravens. • Following this logic: the observation of a white

shoe also confirms the hypothesis

Sir Karl Popper (1902-1994) critical rationalism

Theory-ladenness of data

• A theory is like a flashlight• Everything you shine on you see in the light of

the flashlight.• So confirmation as demarcation criterion

won’t work.

Einstein versus Marx

• Popper wanted to distinguish between real and pseudoscience

• Real science: Newton and Einstein• Pseudoscience: Marx and Darwin

Poppers demarcation criterion

• A theory is scientific if it is logically consistent.• A theory is scientific if it is falsifiable.

Falsification

Falsification

• A theory is like a rule• When falsified the rule is rejected (There are

no ad hoc adjustments)• Some statements are only falsifiable in theory,

while others are even falsifiable in practice.• The more risky a theory, the better the theory

Marxism

• Marx called his ideas science• Popper called the ideas of Marx

pseudoscience• Because uses ad hoc hypotheses

Example

• One notices a white swan. From this one can conclude:– At least one swan is white.

• From this, one may wish to conjecture:– All swans are white.

• If we observe a black swan the theory is falsified.

Problem solved?

• The big six:• carbon, hydrogen, nitrogen, oxygen,

phosphorus, and sulfur• Mono Lake: substitute phosphorus with

arsenic