Philosophy of Science

Emile van der Zeeevanderzee@lincoln.ac.uk

What is Scientific, what is Not?

Example: Hero of today ...

Tiktaalik; 375 million years ago.

Science, Evolution, and CreationismCommittee on Revising Science and Creationism: A View from the National Academy of Sciences, National Academy of Sciences and Institute of Medicine of the National AcademiesISBN: 0-309-10587-0, 88 pages, 8 x 10, (2008)http://www.nap.edu/catalog/11876.html

What is Philosophy of Science?

Questions our intuitions about:

- science/pseudoscience (demarcation criterion)- the (?!) scientific method- progress in science- truth/falsity of theories

Our intuitions are not only questioned, but also formalized and tested.

PositivismPopper

Paradigms

P

P

P

Logical Positivism

Moritz Schlick

Wiener Kreis (1929) manifesto:

- Knowledge is based on nowledge is based on observable factsobservable facts- Unobservable metaphysical elements should not beUnobservable metaphysical elements should not be

part of theories (part of theories (metaphysics = religion ≠ sciencemetaphysics = religion ≠ science))- Goal is Goal is one unified scienceone unified science comprising allcomprising all

statements that can be related to directly observablestatements that can be related to directly observable elementselements

- Only Only logiclogic and and mathematicsmathematics can detect non- can detect non-observable truthsobservable truths (e.g. general statements) via the (e.g. general statements) via the method of logical inductionmethod of logical induction

- A A reductionreduction of concepts, statements and theories to of concepts, statements and theories to directly observable elementsdirectly observable elements

Method of Logical Induction

The derivation of general statements (e.g. laws)from singular statements (observable truths):

John, Mary, Peter, etc. are swans. PremiseJohn, Mary, Peter, etc. are white. Premise All swans are white. Conclusion

The general character of the Method of Induction:

A1, A2, A3 ... An are B.A1, A2, A3 ... An are C.All B’s have the property C.

Logical Positivist stance on

Demarcation:Demarcation:

Science is based on observable facts. PseudoscientificScience is based on observable facts. Pseudoscientific theories contain metaphysical elements.theories contain metaphysical elements.

Progress in science:Progress in science:

Science is cumulative. Current theories contain moreScience is cumulative. Current theories contain more observation statements than theories in the 17observation statements than theories in the 17thth century.century.

Philosophy of Science should promote the inductivistPhilosophy of Science should promote the inductivist method.method.

Problems with the inductivist method

An inductivist turkey observes:

On December 25th

Bob is a turkey, Harry is a turkey, I am a turkey. Bob gets his breakfast at 6am, Pete gets his … etc. All turkeys always get their breakfast at 6am.

Induction is notInduction is not a valid methoda valid method

Other problems with Inductivism/Logical Positivism:

- How many singular statements are necessary?- Under how many circumstances must they be true?- What is the status of counterexamples?- What is the status of non-directly observable ‘facts’ that make theories work (gravity, quarks)?- What is the status of inexact evidence?

So ....So ....

It is not possible to It is not possible to proveprove that a theory is true that a theory is true(based on the inductive method)(based on the inductive method)

Heritage:Heritage:

Facts - Direct observationsFacts - Direct observationsTheories - A set of statements that organise, predictTheories - A set of statements that organise, predict and explain observationsand explain observationsPredictions - Drawing inferences from theories toPredictions - Drawing inferences from theories to predict Factspredict FactsLaws - Empirical GeneralisationsLaws - Empirical GeneralisationsModels - Concrete instantiations of theoryModels - Concrete instantiations of theory(specifying a working mechanism)(specifying a working mechanism)

Falsificationism

... Einstein consciously seeks for error elimination. He tries to kill his theories: he is consciously critical of his theories which, for this reason, he tries to formulate sharply rather than vaguely

Karl R. Popper (1972, 1979). Objective Knowledge; An evolutionary approach (revised edition). Oxford, Uk: Oxford University Press. pages 7 and 24-25.

We cannot (logically) prove that theories are true, but we can prove – deductively - that they are false:

All ravens are black (universal statement)A non-black raven was observed (singular statement)It is not the case that all ravens are black

(universal statement falsified)

This deduction is logically valid.

• only objective knowledge can be criticized, and subjective knowledge only in as far as it can be made objective

• the more often a theory escapes falsification, the more this theory is corroborated

Consequences of the above

(1) For the way we look at theories:

• scientific theories are falsifiable, but non-scientific theories are not

• theories must be formulated as precisely as possible, in order to make them as falsifiable as possible

• Theory A is more informative than theory B if A excludes more observation statements than B.

The mosaic virus only affects tobacco plants in Lincoln (precise, but not informative).

Mosaic viruses affect tobacco plants everywhere – if conditions x, y, z are met (informative, and precise).

(2) The growth of scientific knowledge :

• ... science starts with problems, not observations. „Problems crop up ... when we are disappointed in our expectations, or when our theories involve us in difficulties, in contradictions ...“ (In: The Growth of Scientific Knowledge (1960))

• the mechanism of the growth of scientific knowledge is conjecture and refutation

• the conjectures must not be too bold (because then we learn nothing if they are refuted)

• the most important moments in the growth of knowledge are theory falsifications

The growth of scientific knowledge can be schematised as follows:

t1 ------> problems with t1 ------> test t1 ------> falsify t2 ... etc.

t1 can be based on our intuitions (evolution has ‚baked in’ a certain range of things that we expect).

• every change in a theory must have testable consequences. If this is not the case, the new theory is an ad-hoc theory.

E.g., animals do have language. Every time I try to test this, it doesn’t work though. Maybe they get nervous, and can’t perform. Maybe I can’t test it, but it’s true; really ...........

Problems with Falsificationism

• If a theory appears to be falsified, the theory may be at fault, but also the observation statements (the ‘facts’) on which we base the falsification. (Observation statements are also based on theories).

• Not all aspects of a theory are falsifiable. Every theory contains metaphysical assumptions (e.g. that the phenomena under investigation exist).

• Do we abandon a theory after one falsification? Two, three, etc?

• What do we do when a theory is falsified, but we don’t have any better ideas?

Paradigm Approach

Thomas Kuhn

Evolution of science not cumulative, but revolutionary:

Pre-scientific periodNormal Science (a Paradigm)CrisisRevolution (a Paradigm shift)Normal Science again

Pre-scientific period

• there are as many theories as there are scientists• there is no shared idea about the basics• all research ‘starts from scratch’• it is not clear what observations are relevant

Beginning of psychology: Mixture of philosophy, physiology, anthropology, linguistics, optics, etc.

Beginnings of chemistry: alchemy, industrial applications, etc.

Normal Science (Paradigm)

• it is not possible to define a paradigm

• shared metaphysical ideas• accepted theoretical assumptions and laws• set of techniques and technical apparatuses• applying known theories and techniques to as many

aspects of nature as possible• trying to find solutions for falsifications within the

paradigm• puzzles for which there is no solution are anomalies

(not falsifications)• the Paradigm is not criticised• students learn the paradigm by learning the

techniques, and what the relevant observations are

Crisis

• anomalies are serious if their number is big or if they go against the basics of the paradigm/ the world view

• philosophical debates about the basics• things grow worse if a new paradigm appears

Behaviorism. Experiments that showed that instincts stood in the way of conditioning. Theoretical critique by Chomsky on Skinner’s theory of language.

Revolution

• some day some scientist develops a new view on certain problematic phenomena, thereby discarding the old view (a Gestalt switch)

• scientists adhering to the old paradigm either make the Gestalt switch, or are marginalized, and die out.

Chomsky/Skinner.

So, what is scientific?

All findings, procedures, etc. that are part of a period of Normal Science.

Problems with the Paradigm Approach

• Is normal science really just a fashion?• Do scientists belonging to different paradigms really

live in different worlds? If so, mutual criticism is impossible, only persuasion is.

• Paradigms can not be compared to each other, because paradigms are incommensurable; so, we can not determine what paradigm is better than another one

• What is true or not depends on the paradigm one adheres to

What’s in it for you?

Integrating most elements: the Empirical Cycle

De Groot, 1961

Observations (theoretically inspired)

Evaluation (of results/theories)

Induction(theory formation)

Deduction(of hypotheses)

Testing(of hypotheses)

Summary

- theory neutral observations/statements do not exist

- theories cannot be proven- theories can be falsified- theories are linked to other theories

One should strive for:

- theories that can be tested- theories that formulated precisely- theories that have a maximum level of

information contents (generalisation)- theories that are not ad-hoc (i.e. do not lead to

new – independent – testing)

In relation to your project

- does the theory that you base yourself on allow you to make clear predictions (i.e. predictions with a clear outcome; a instead of b)?

- does the theory that you base yourself on allow you to falsify it?

- can you formulate the exact conditions under which the theory can be tested?

- did you leave any escape routes for the theory (any interpretations under which it can still escape falsification; ie is your method/design safe and sound)?

More background information

Hillary Putnam on the Philosophy of Science: part II (11 minutes)

Why can’t objective facts exist?Is it possible for science to find the truth?

Hillary Putnam on the Philosophy of Science: part of part III (11 minutes)

What is science, and what is not science?Why is the inductive method not possible?What is THE SCIENTIFIC METHOD?

Advised Reading Materials

Chalmers, A. F. (1999). What is this thing called Science? (3rd edition). Open University Press.