Philosophy of Science
Emile van der Zee
evanderzee@lincoln.ac.uk
What is Scientific, what is Not?
Example: Hero of today ...
Tiktaalik; 375 million years ago.
Science, Evolution, and Creationism
Committee on Revising Science and Creationism: A View from the National Academy of
Sciences, National Academy of Sciences and Institute of Medicine of the National Academies
ISBN: 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.
P
P
P
Positivism
Popper
Paradigms
Logical Positivism
Moritz Schlick
Wiener Kreis (1929) manifesto:
- Knowledge is based on observable facts
- Unobservable metaphysical elements should not be
part of theories (metaphysics = religion ≠ science)
- Goal is one unified science comprising all
statements that can be related to directly observable
elements
- Only logic and mathematics can detect nonobservable truths (e.g. general statements) via the
method of logical induction
- A reduction of concepts, statements and theories to
directly 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. Premise
John, 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:
Science is based on observable facts. Pseudoscientific
theories contain metaphysical elements.
Progress in science:
Science is cumulative. Current theories contain more
observation statements than theories in the 17th
century.
Philosophy of Science should promote the inductivist
method.
Problems with the inductivist method
An inductivist turkey observes:
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.
On December 25th
Induction is not
a 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 ....
It is not possible to prove that a theory is true
(based on the inductive method)
Heritage:
Facts - Direct observations
Theories - A set of statements that organise, predict
and explain observations
Predictions - Drawing inferences from theories to
predict Facts
Laws - Empirical Generalisations
Models - Concrete instantiations of theory
(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 period
 Normal Science (a Paradigm)
 Crisis
 Revolution (a Paradigm shift)
 Normal Science again
 Pre-scientific period
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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
Observations
(theoretically
inspired)
Evaluation (of
results/theories)
Induction
(theory
formation)
Testing
(of
hypotheses)
Deduction
(of
hypotheses)
De Groot, 1961
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.