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History and Philosophy of Science

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Title: History and Philosophy of Science


1
History and Philosophyof Science
  • Lecture 2

2
History and Philosophy of Science
The history and philosophy of science can inform
our research in science informatics by providing
  • theories of explanation and scientific knowledge
  • views of discovery and justification in the
    sciences
  • perspectives on scientific progress and the
    distinction between normal and revolutionary
    science
  • narratives that reflect actual scientific
    practice and needs and
  • case studies to inspire novel informatics
    capabilities.

As a result, a foundation in history and
philosophy can lead us toward general informatics
solutions as opposed to systems that address ad
hoc, problem-specific scenarios.
3
The Concerns of the Philosophy of Science
Philosophy of science is a broad discipline that
investigates the concepts, activities, and
interaction of scientists, including
  • the structure of scientific explanations
  • the form of scientific methodology
  • the methodology of scientific justification
  • the context of scientific discovery and
  • the nature of scientific progress.

Although other topics also arise, the listed ones
are the most relevant to science informatics.
4
Scientific Explanation
Scientific explanations emphasize the reasons why
an event happened rather than a description of
the event itself. In practice, scientific
explanations combine situation specific
conditions with general principles expressed as
  • logical sentences
  • mathematical equations
  • qualitative graphic or linguistic accounts
  • computer programs and other forms.

Much of this work began with Carl Hempel and Paul
Oppenheims Studies in the Logic of Explanation
from 1948.
5
Deductive-Nomological Explanation
This view treats scientific explanations as
deductive arguments where initial conditions and
general laws imply observations.
C1, C2, ..., Cm L1, L2, ..., Ln -----------------
--- E
Statement of antecedent conditions
Logical Deduction
Statement of general laws
Description of the empirical phenomenon to be
explained.
Schema taken from Hempel and Oppenheims 1948
paper.
6
Deductive Reasoning
Logical deduction is often characterized by modus
ponens
If P, Then Q P --------------------Q
Mapping to the DN view of explanation, If P,
then Q general laws P the
set of antecedent conditions Q the
event to be explained. Laws may be expressed in
other formalisms (e.g., mathematical equations),
but there must be a mechanism to infer their
consequences from observations.
7
Hypothetico-Deductive Method
Popularized by William Whewell in the 1800s, this
view of the scientific method consists of two
stages of activity.
Discovery refers to those processes that lead to
the statement of a conjecture based on
observations.
Justification concerns the evaluation and
acceptance of scientific knowledge once stated.
Whewell posited three conditions for
justification
  1. The hypothesis must predict unseen phenomena of
    the type that it was meant to explain.
  2. The hypothesis must help explain phenomena of a
    new type.
  3. The hypothesis must fit within a theory that
    becomes more coherent (unified, simple, etc.)
    over time.

8
Karl Popper and Falsification
A focus on confirmation raises Humes problem of
induction. That is, past evidence may not be
indicative of future events. Popper suggests a
focus on falsification where scientists seek to
refute their hypotheses through
experiment. Falsificationism posits that one
cannot prove theories or hypotheses true, or even
probable. Under this view, hypotheses are either
false or corroborated. Poppers philosophy
required the sciences to establish falsifiable
hypothesesanything else is pseudoscience.
9
Scientific Discovery
Philosophers largely ignored scientific
discovery, believing it to be immune to logical
or heuristic analysis. Popper wrote
The initial stage, the act of conceiving or
inventing a theory, seems to me neither to call
for logical analysis nor to be susceptible of it.
The question how it happens that a new idea
occurs to a manmay be of great interest to
empirical psychology but it is irrelevant to the
logical analysis of scientific knowledgeMy view
may be expressed by saying that every discovery
contains an irrational element, or a creative
intuition
Popper was not alone in his views. Hempel among
others believed in the irrationality of discovery.
In the latter part of the 20th century,
philosophers, psychologists, and a new breed,
artificial intelligence researchers, posited
induction and abduction as a means to mechanize
discovery.
10
Inductive Reasoning
Inductive reasoning identifies specific
commonalities across several events and posits a
corresponding general claim.
Q1 is P Q2 is P Qm is P -------------------- All
Qs are P
Evidence Claim
The claim is not justified logically and is at
best supported statistically. Some consider
induction useful only for evaluation.
11
Abductive Reasoning
Abductive reasoning involves explaining an event
by positing a statement that, if true, would
manifest that event.
If P, Then Q Q --------------------P
Theory Event Hypothesis
In the schema above, we observe event Q and we
know that if some hypothesis P were true, we
could explain Q, so we infer P.
Charles Peirce discussed abduction in detail and
claimed that it was the sole source of new ideas
in science.
12
Scientific Progress Kuhn
Thomas Kuhn distinguished between two types of
science.
Normal science involved puzzle solving activity
that revolved around some current scientific
theory.
Revolutionary science arose when anomalies
overwhelmed the prevailing theory and scientists
searched for a new paradigm.
Notably Kuhn believed that each new paradigm
signifies progress by increasing in scope and, in
particular, by
  • explaining most of the anomalies driving the
    paradigm shift
  • accounting for most of the phenomena covered by
    the old paradigm

13
Scientific Progress Lakatos
Imre Lakatos posited two types of knowledge in a
theory
The hard core consisted of those ideas central to
a research programme that one refuses to refute
based on observation.
The protective belt of auxiliary hypotheses that
may be modified in the face of anomalies.
For Lakatos, a research programme is more
permanent than a theory since it is tied to the
core while the belt may change.
Anomalies do not drive the revision of research
programmes. Instead, science progresses to new
programmes when
  • the current programme no longer produces new
    ideas
  • the new programme explains the success of the
    current one and has greater explanatory power.

14
History of Science
The history of science is an empirical field that
investigates
  • the methodological practices,
  • the personal characteristics, and
  • the social pressures

that contribute to scientific activity.
Thomas Kuhn wrote, historical study can yield
a new sort of understanding of the structure and
function of scientific research.
More specifically, the history of science can
identify the role of
  • scientific data,
  • scientific knowledge, and
  • scientific communities

in everyday discoveries and in revolutionary
shifts.
15
Importance of New Kinds of Data
Scientific discoveries often grow out of new
methods for data collection and new types of
data. Consider
  • Lavoisiers emphasis on weight and measurements
  • Brahes regular observations of celestial
    objects
  • Darwins observations of animals across the
    planet and
  • Franklins x-ray diffraction images of DNA
    structure.

These advances required a combination of
technical skill and an appreciation of empirical
rigor.
Notably Lavoisier and Darwin profited from their
data, whereas Brahe and Franklins observations
led others to discoveries.
16
Chemistry Antoine Lavoisier
Lavoisier revolutionized the methods and theory
of chemistry.
While his contemporaries primarily observed and
described the changes in chemical substances,
Lavoisier valued measurement.
Weighing objects within a bell jar before and
after combustion revealed the conservation of
mass contrary to appearance.
This finding ultimately led to the discovery of
oxygen and the rejection of the phlogiston theory.
17
Astronomy Tycho Brahe
Brahes legacy are his systematic astronomical
measurements that were more accurate than any
others available at the time.
His contribution reflected meticulousness and
ingenuity in
  • inventing and improving scientific instruments
  • inspecting and calibrating his instruments
    routinely and
  • stressing systematic and regular measurements of
    astronomical objects.

Although Brahe worked on his own geocentric model
of the solar system, Johannes Keplers analysis
of the data ultimately produced an accurate
heliocentric model of planetary orbits.
18
Role of Theories and Models in Science
Theories and models hold a special place in
scientific activity
  • they define the scope and focus of scientific
    investigation
  • they support predictions about experimental
    outcomes and future observations and
  • they establish world views subject to challenge.

The history of science illustrates these roles.
For example,
  • Darwins theory of evolution suggested the search
    for a mechanism of transmission
  • the periodic table lets chemists predict
    elemental properties
  • Newtonian physics led to the discovery of Neptune
    and Ceres
  • aesthetic values led to the rejection of
    Ptolemaic theory.

19
Periodic Table of Elements
Used to illustrate and predict elements and their
properties.
20
The Discovery of Neptune
After predicting the orbit of Uranus using
Newtonian theory, Alexis Bouvard noticed
irregularities in its observed orbit.
Bouvard conjectured that an unknown planet was
causing the discrepancy, but did not investigate.
John Adams and Urbain Le Verrier became
independently aware of Bouvards findings and
eventually competed for the discovery.
Both Le Verrier and Adams applied Newtonian
theory and Bodes law to predict the location of
the new planet. Ultimately Le Verriers
predictions led to the discovery of Neptune.
with considerable controversy
21
Ptolemy and Copernicus
Ptolemys geocentric theory of the universe
dominated Western science (and religion) for
centuries.
This theory has planets moving in nested circular
motions that are uniform around an equant.
Copernicus considered the equant abhorrent as it
violated the tenet that planets travel at uniform
speeds around circular trajectories.
He developed a new, heliocentric theory that,
although no more accurate and no less complex,
removed the equant.
22
Scientific Communities
In principle, communities of scientists serve
several purposes. For instance, they
  • transmit ideas across physical and disciplinary
    boundaries,
  • collaborate on research topics too large for any
    one lab,
  • motivate members through the competition for
    discovery, and
  • evaluate the merit of ideas and protect against
    fraud.

A scientific community has elements of enablement
and suppression. History has shown scientists as
progressively entertaining new ideas, but
conservative in their acceptance.
23
Watson, Crick, and Everyone Else
Watson and Crick are almost synonymous with the
discovery of DNA, but other groups worked
simultaneously
  • Linus Paulings laboratory at Caltech and
  • Maurice Wilkins and Rosalind Franklin at Kings
    College.

The atmosphere was competitive, but the discovery
of DNAs structure was the combined work of
several individuals, including
  • William Bragg, Watson and Cricks supervisor
  • Alfred Hershey and Martha Chase, who identified
    DNA (in opposition to proteins) as the genetic
    material
  • Edward Ronwin, whose 1951 paper rekindled
    Paulings interests in DNA structure and many
    others.

In this case, the community was largely
supportive of what was ultimately a work of
scientific progress.
24
Wegener and Continental Drift
Alfred Wegener proposed his theory of continental
drift in 1912 when the dominant theory held that
land mass was shaped by the cooling of the earth.
Wegeners observational evidence was strong, but
his proposed mechanism was untenable the very
idea required scientists to abandon decades of
theory.
Empirical discoveries in the 1950s led to plate
tectonics as a mechanism that supported many of
Wegeners claims.
Although Wegeners theory was initially
entertained as reasonable, eventually the
scientific community became openly hostile,
suppressing progress for decades.
25
Scientific Revolutions
One can view the history of science as successive
revolutions that dramatically alter scientific
concepts and mechanisms
  • Wegeners theory of continental drift transformed
    geology
  • Copernicus heliocentric theory transformed
    astronomy
  • Lavoisiers oxygen theory transformed chemistry
  • Newtons theory of physics displaced the
    Cartesian model
  • Einsteins theories revolutionized Newtonian
    physics
  • Skinners behaviorist movement transformed
    psychology
  • Chomsky, Miller, Newell, Simon, and others
    overthrew behaviorism for a renewed cognitive
    psychology.

These revolutions occur within the context of
history and are driven by methodological,
personal, and social forces.
26
History and Philosophy of Science
The history and philosophy of science plays a
dual role for informatics research.
Philosophy of Science provides theories about how
science should or does function that informatics
researchers can appeal to as general principles
for interactive systems.
History of Science provides data with which those
researchers can evaluate theories of science and
abduce new explanations for observed courses of
behavior.
Together this rich context can lead us toward
general informatics systems that benefit a broad
range of scientific researchers.
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