History and Philosophyof Science

Lecture 2

History and Philosophy of Science

• 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.

The history and philosophy of science can inform our research in science informatics by providing

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.

The Concerns of the Philosophy of Science

• 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.

Philosophy of science is a broad discipline that investigates the concepts, activities, and interaction of scientists, including

Although other topics also arise, the listed ones are the most relevant to science informatics.

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 Oppenheim’s Studies in the Logic of Explanation from 1948.

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

Schema taken from Hempel and Oppenheim’s 1948 paper.

Statement of general laws

Description of the empirical phenomenon to be explained.

LogicalDeduction

Deductive Reasoning

Logical deduction is often characterized by modus ponens:

If P, Then QP

--------------------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.

Hypothetico-Deductive MethodPopularized by William Whewell in the 1800s, this view of the scientific method consists of two stages of activity.

Justification concerns the evaluation and acceptance of scientific knowledge once stated.

Discovery refers to those processes that lead to the statement of a conjecture based on observations.

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.

Karl Popper and Falsification

A focus on confirmation raises Hume’s 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.

Popper’s philosophy required the sciences to establish falsifiable hypotheses—anything else is pseudoscience.

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 man…may be of great interest to empirical psychology; but it is irrelevant to the logical analysis of scientific knowledge…My 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.

Inductive Reasoning

Q1 is PQ2 is P

…Qm is P

--------------------All Q’s are P

Evidence

Claim

Inductive reasoning identifies specific commonalities across several events and posits a corresponding general claim.

The claim is not justified logically and is at best supported statistically. Some consider induction useful only for evaluation.

Abductive Reasoning

If P, Then QQ

--------------------P

Abductive reasoning involves explaining an event by positing a statement that, if true, would manifest that event.

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.

TheoryEvent

Hypothesis

Charles Peirce discussed abduction in detail and claimed that it was the sole source of new ideas in science.

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

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.

• the current programme no longer produces new ideas• the new programme explains the success of the current one

and has greater explanatory power.

Anomalies do not drive the revision of research programmes. Instead, science progresses to new programmes when

History of Science

• the methodological practices, • the personal characteristics, and • the social pressures

The history of science is an empirical field that investigates

Thomas Kuhn wrote, “historical study [can] yield a new sort of understanding of the structure and function of scientific research.”

that contribute to scientific activity.

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.

Importance of New Kinds of Data

• Lavoisier’s emphasis on weight and measurements;• Brahe’s regular observations of celestial objects;• Darwin’s observations of animals across the planet; and• Franklin’s x-ray diffraction images of DNA structure.

Scientific discoveries often grow out of new methods for data collection and new types of data. Consider

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 Franklin’s observations led others to discoveries.

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.

Astronomy: Tycho Brahe

• inventing and improving scientific instruments;• inspecting and calibrating his instruments routinely; and• stressing systematic and regular measurements of

astronomical objects.

Brahe’s legacy are his systematic astronomical measurements that were more accurate than any others available at the time.

His contribution reflected meticulousness and ingenuity in

Although Brahe worked on his own geocentric model of the solar system, Johannes Kepler’s analysis of the data ultimately produced an accurate heliocentric model of planetary orbits.

Role of Theories and Models in Science

• 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.

Theories and models hold a special place in scientific activity:

• Darwin’s 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.

The history of science illustrates these roles. For example,

Periodic Table of Elements

Used to illustrate and predict elements and their properties.

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 Bouvard’s findings and eventually competed for the discovery.

Both Le Verrier and Adams applied Newtonian theory and Bode’s law to predict the location of the new planet. Ultimately Le Verrier’s predictions led to the discovery of Neptune.*

* with considerable controversy

Ptolemy and Copernicus

Ptolemy’s 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.

Scientific Communities

• 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.

In principle, communities of scientists serve several purposes. For instance, they

A scientific community has elements of enablement and suppression. History has shown scientists as progressively entertaining new ideas, but conservative in their acceptance.

Watson, Crick, and Everyone Else

• Linus Pauling’s laboratory at Caltech and • Maurice Wilkins and Rosalind Franklin at King’s College.

Watson and Crick are almost synonymous with the discovery of DNA, but other groups worked simultaneously:

The atmosphere was competitive, but the discovery of DNA’s structure was the combined work of several individuals, including• William Bragg, Watson and Crick’s supervisor;• Alfred Hershey and Martha Chase, who identified DNA (in

opposition to proteins) as the genetic material;• Edward Ronwin, whose 1951 paper rekindled Pauling’s

interests in DNA structure; and many others.

In this case, the community was largely supportive of what was ultimately a work of scientific progress.

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.

Although Wegener’s theory was initially entertained as reasonable, eventually the scientific community became openly hostile, suppressing progress for decades.

Wegener’s 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 Wegener’s claims.

Scientific Revolutions

• Wegener’s theory of continental drift transformed geology;• Copernicus’ heliocentric theory transformed astronomy;• Lavoisier’s oxygen theory transformed chemistry;• Newton’s theory of physics displaced the Cartesian model;• Einstein’s theories revolutionized Newtonian physics;• Skinner’s behaviorist movement transformed psychology;• Chomsky, Miller, Newell, Simon, and others overthrew

behaviorism for a renewed cognitive psychology.

One can view the history of science as successive revolutions that dramatically alter scientific concepts and mechanisms:

These revolutions occur within the context of history and are driven by methodological, personal, and social forces.

History and Philosophy of Science

The history and philosophy of science plays a dual role for informatics research.

History of Science provides data with which those researchers can evaluate theories of science and abduce new explanations for observed courses of behavior.

Philosophy of Science provides theories about how science should or does function that informatics researchers can appeal to as general principles for interactive systems.

Together this rich context can lead us toward general informatics systems that benefit a broad range of scientific researchers.