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Scientific Methodology PH351F/PH451F
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7.1 Overview (what we do in these two lectures) ... Then, we will apply this new methodology to the historical case of the Copernican revolution. ... – PowerPoint PPT presentation
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Title: Scientific Methodology PH351F/PH451F
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Scientific Methodology PH351F/PH451F
- Luca Moretti
- Department of Philosophy
- Aberdeen University
- l.moretti_at_abdn.ac.uk
- http//lucamoretti.org
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Lecture 7Lakatos methodology I
- Requested readings
- I. Lakatos, Falsificationism and the methodology
of scientific research programmes in his
Philosophical Papers, vol 1, pp. 31-52, pp.
68-73, and pp. 86-90.
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7.1 Overview (what we do in these two lectures)
- I will first outline Lakatos methodology of
scientific research programs. - Then, I will apply this new methodology to the
historical case of the Copernican revolution. - I will briefly describe the Ptolemaic research
program and the Copernican research program. - We will learn why, according to Lakatos, the
second became rationally preferable to the first
in the first half of the XVII century. - Although Lakatos explanation is illuminating, it
is not completely convincing. - The problem of explaining the Copernican
revolution from the point of view of scientific
methodology remains partly open. - Some of the problems depend on Feyerabends sharp
criticism of Lakatos view.
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7.2 Lakatos project
- Lakatos aims essentially to provide a
reformulation of falsificationism capable to
lessen the subjective and arbitrary elements of
Poppers methodology, which were introduced to
cope with the Duhem-Quine thesis. - For Popper, a theory can be considered falsified
and thus eliminated on the grounds of
incompatible observations when the scientific
community unanimously stipulates (?) that the
(well corroborated) auxiliary assumptions
necessary for the falsification are true. - Since any well corroborated auxiliary assumption
might prove false, true theories might be
eliminated! - To avoid methodological anarchism (i.e. the view
that no theory can ever be eliminated), Poppers
falsificationism would seem to turn science into
an arbitrary enterprise. - Lakatos intends to re-formulate falsificationism
to the effect that the elimination of theories
does not rest on subjective decisions but is
empirically justified. - This requires focusing, not on theories, but on
research programs conceived of as dynamic
sequences or progressions of theories.
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7.3 The decisions necessary to falsify a theory
for the falsificationist
- On Poppers falsificationism (at least in
Lakatos interpretation of it), scientists can
falsify a theory on the grounds of observations
only after taking certain methodological
decisions. - There are three types of decisions (or
assumptions) - (i) Decisions about which type of statements are
observation statements - As the range of what is observable has vague
boundaries (something observable only by
telescope is really observable?), a specific
class of statements should be assumed to be the
one of the observation statements. - (ii) Decisions about which asserted observation
statements are true - This requires deciding that the tools (e.g.
telescopes) used to make the relevant
observations are reliable tools. - This in turn requires deciding that the theories
about these tools are correct (e.g. optics).
These theories must be corroborated by
independent tests. - This also involves deciding that the conditions
of correct functioning of the relevant
observation instruments (e.g. absence of high
temperature) are satisfied in the specific cases.
These conditions must have been repeatedly
checked. - Finally, the accepted observations must have been
repeated several times.
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7.4 The decisions necessary to falsify a theory
for the falsificationist
- (iii) Decisions about which theories are
falsified by true observational statements - Suppose T (e.g. a theory of comets) entails O
(e.g. The comet C will be seen in x at time t).
Suppose Not-O is true. in this case O is false! - T entails O only in conjunction with auxiliary
assumptions specifying at least - The initial conditions (A1) (e.g. the location
of C in the past). - That there is no disturbing factor (A2) (e.g.
no body close to C that disturbs C motion). - That the observation tools are reliable (A3)
(e.g. telescope is reliable). - To conclude that the falsification of O, entailed
by T A1 A2 A3 does falsify just T,
scientists have to assume that A1, A2 and A3 are
all true. - A3 has been already considered while speaking
of decisions of type (ii). - Scientists will assume that A1 is true after
repeated tests of it. - Scientists will assume that A2 is true after
testing many conjectures about possible
influencing factors.
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7.5 Lakatos objections to falsificationism
- According to Lakatos, falsificationism is
affected by two general problems - (a) Falsificationism asks scientists to take
decisions that may prove misleading. - Popper seems to think of that these decisions
are irreversible. - Popper wants to secure the possibility of
rejecting some theories to - allow for the possibility of scientific
progress, but the risk is rejecting - the wrong theories!
- (b) Falsificationism does not reflect what
scientists really do. - In particular
- The history of science shows that the
methodological decisions of - type (i), (ii) and (iii) are continuously
questioned and re-discussed in time. - Real scientists are much slower and more prudent
than Popper believes. - Furthermore, real science is more complex than
in Poppers picture because scientific disputes
typically involve not one theory but two rival
theories. - For instance
- Ptolemys theory versus Copernicus theory,
- Cartesian mechanics versus Newtonian mechanics,
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7.6 How Falsificationism should be reformed
according to Lakatos
- Lakatos proposes the following rules
- (Theory acceptance) A new theory T should be
accepted if and only if (a) the unrefuted (but
not the refuted) predictions of its immediate
predecessor T are derivable from T, (b) T
makes new predictions with respect to T, (c) some
of these new predictions are verified. - (Theory rejection) A theory T should be rejected
if and only if there is new theory T such that
(a) the unrefuted (but not the refuted)
predictions of T are derivable from T, (b) T
makes new predictions with respect to T, (c) some
of these new predictions are verified. - Note that the falsification of T is neither
sufficient nor necessary for the rejection of T. - It is not sufficient because T cannot be rejected
on the grounds of incompatible observation
statements if no better theory T is available. - It is not necessary because T can be rejected
just because there is a new theory T with
additional and verified predictions. - Note also that the new theory T can be accepted
even if some of its new predictions prove false.
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7.7 How falsificationism should be reformed
according to Lakatos
- To lessen the arbitrary or subjective component
of falsificationism and to explain how
methodological decisions are continuously
re-discussed by scientists, the rules of
acceptance and rejection should be applied to
theories in conjunction with all their auxiliary
assumptions. - Let us call the theories of this type theoretical
systems or just systems. - Consider a series of systems S1, S2, S3, of
this type, and suppose that each system results
from changing only the auxiliary assumptions of
the former system in order to accommodate its
empirical anomalies. - A series of this type is theoretically
progressive if each system in the series makes
new predictions. - A theoretically progressive series is also
empirically progressive if, for each system in
the series, some of the new predictions are
verified. - A series of systems that is both theoretically
progressive and (at least intermittently)
empirically progressive is said progressive,
otherwise it is said degenerating. - Note that if a series of systems is progressive,
it has been constructed in perfect accordance
with Lakatos rules of theory acceptance and
rejection (applied to systems).
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7.8 How falsificationism should be reformed
according to Lakatos
- Lakatos suggests that, to cope with
falsifications, scientists should construct (and
that they do construct) a series of systems of
this kind in which the auxiliary assumptions are
continuously modified with the purpose of making
the series progressive. - (Note that this seems to correspond to what Kuhn
calls puzzle solving activity of scientists,
which characterises normal science). - For instance, consider a system S equivalent to
the conjunction T A1 A2 A3, where A1, A2
and A3 are the auxiliary assumptions. Suppose
that S entails the observational statement O,
which turns out to be false. - In this case, S is false too.
- To cope with the falsification of S, the
scientists will modify A1, A2 or A3 to prevent
the deduction of O, but they will try not to
touch the theory T, central to the whole system. - Modifications of A1, A2 or A3 are tolerable as
non-ad hoc if they make the series of
succeeding systems at least theoretically
progressive. - Any series of systems which is not at least
theoretically progressive should be considered
pseudoscientific.
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7.9 How this makes falsificationism less arbitrary
- If falsificationism is reformulated in this
fashion, the only arbitrary decisions that
scientists have to take concern the
identification of the class of the observation
statements. - All other assumptions and decisions of scientists
will be empirically tested again and again, and
so (to a good extent) justified, while developing
the series of systems to cope with
falsifications. - Suppose again T (e.g. a theory of comets) entails
O (e.g. The comet C will be seen in x at time
t) in conjunction with the auxiliary assumptions
specifying - (A1) The initial conditions. (Earlier locations
of C). - (A2) That there is no disturbing factor. (No
unknown body is close to C). - (A3) That the observation tools are reliable.
(Telescope is reliable). - Suppose O is false.
- To cope with this falsification, scientists will
replace A1, A2 and A3 in turn with alternative
assumptions and they will test each new systems
so obtained. - Any rejected auxiliary can always be reconsidered
in combination with new auxiliaries - The ideal goal is to maintain the sequence of
systems progressive.
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7.10 Lakatos demarcation criterion
- While Poppers demarcation criterion focuses on
single theories (a theory is scientific if and
only if it could be falsified by observations
describable with precision in advance), Lakatos
demarcation criterion focuses on sequences of
theories or systems - Any series of systems which is not at least
theoretically progressive is pseudoscientific. - One can already guess from this why Lakatos
thought that the scientists were rationally
justified in switching from the old Ptolemaic
view of the heavens to the new Copernican. - No system of the series
- Eudoxus theory -gt Apollonius theory
-gt Hipparchus theory -gt Ptolemys theory
- probably predicted any new fact.
- The whole series became very soon
pseudoscientific an enormous sequence of ad-hoc
adjustments. - This explains Copernicus feeling that the
Ptolemaic system was nothing but a (rational)
monster.
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- End Lecture 7
