Upload
stephanie-wade
View
218
Download
0
Tags:
Embed Size (px)
Citation preview
CSC 599: Computational Scientific Discovery
Lecture 2:
Philosophy of SciencePost-Logical Empiricists
Outline
Problems with Logical EmpiricismPhilosophy of Science Post-Logical Empiricism
Thomas Kuhn Imre Lakatos Larry Laudan Sociologies of science Model-base philosophies of Ronald Giere
Differences between CSD and Philosophy of Science
What shall we conclude from all of this?
Problems with Logical Empiricism
Problems with verification criterion Ayer, Popper
Problems with reductionism Quine
Problems with language Quine, Maxwell and Goodman
Problems with removing science from historical context
Philosophy of Science in the Anglophone world in the 1960sLogical Empiricism “This is science”/ “This isn't science” By people who aren't even scientists (a bit arrogant, isn't it?)
Other ways to characterize science: Historically
“What have scientists done in past?” Sociologically
“What are scientists doing now?”
Thomas Kuhn andthe Historical Perspective
Kuhn was a theoretical physics student assigned to teach course on ancient science
Suppose your job was to teach some ancient science, like mechanics circa 300 B.C.E.
Perhaps you might . . .1. Get into their mindset2. Study their worldview3. Solve problems the way they conceived of them
2: Study their worldview
2 Realms Terrestrial: Below the moon
Linear motion Celestial: Above the moon
Circular motion
Five elements: Ether (Purely celestial) Fire Air Water Earth
(Rises)
(Sinks)
3. Solve problems the way they conceived them
Motion due to elements out of their place Fire rises Smoke (= fire + air), so it rises too Water flows down
Rain Rivers flow down to the sea
Earth Further down than the water Riverbeds, seabeds
No more reason motive force when an element is at its natural level
Kuhn's Insight
To the ancients, their science made sense! Largely self-consistent Explanatory (smoke rises) Predictive (What happens when you throw a rock
in the air? In water?)
Individual ideas should NOT be understood divorced from context Geocentrism 5 elements Natural motion is at-rest with same element
Part of a larger worldview
Kuhnian Paradigm
A self-consistent worldview, specifies which data are relevant laws are allowable experiments make sense to try theory make sense
Paradigms have: Exemplars
This is how you solve the problem E.g. Harmonic oscillator = mass + spring
Training networks that indoctrinate people into a way of thinking
Kuhn's View of Science(Normal Science)
Problem solving There are always problems
Predictions that can't be done Predictions that come out wrong Discrepancies, inconsistencies (“anomalies”)
Use the techniques culturally allowed by the current paradigm
Can NOT just do anything Must solve the problems of the paradigm with the
paradigm
What most scientist do most of the time
Kuhnian Revolution
Problems always accumulate Crisis = set of major problem(s) not solvable in old
paradigm Eventually some scientists try to invent new
paradigm in which they can be solved
All paradigms are incommensurate! Two competing paradigms have their own view of:
What the important problems are What counts as “data” What explanations look like
No way to objectively say one is better than other
What Kuhn Gives Up
Any notion of “rational progress” Would need some objective vantage point to
compare two paradigms As humans we don't have that
Old paradigms only abandoned when its old-fogey adherents die-off
Newtownian physics is just different that Relativity
What Kuhn Gains
Agreement with a lot of history Many examples of Revolutions
Phlogiston vs. Oxygen Geocentric vs. Heliocentric
Many examples of old paradigms dying only when there obstinate practitioners die off Priestley never accepted Lavoisier's oxygen Lord Kelvin never accepted electromagnetic
theory
Back to Our Example
Ancient vs. Modern PhysicsModern Physicist “Our physics is better because
we can predict the phases of Venus”Ancient Physicist “I don't believe you. All things
in heavenly orbs are perfect spheres”Modern “Our notion of elements is better than
yours too. We can predict chemistry and spectroscopy”
Ancient “So? We predict their motion and stillness!”
What do you think?
Allied Approaches
In 1960s and 1970s people wanted Kuhnian agreement with history Logical Empricist notion of “rational progress”
Allied Approahes Lakatos Laudan
Imre Lakatos
Born Imre Lipschitz in Hungary (1922) Jewish Degree in math, physics and philosophy, 1944 Changed name to Imre Molnár to avoid Nazis
Mother, grandmother, killed in Auschwitz Communist during WWII Changed name to “Lakatos” (= Locksmith)
Honors Geza Lakatos (Hungarian general) Falling out with communists in early 1950s Fled to England after Soviet Union invaded in
1956
Imre Lakatos
Research programmes: Hard core + Auxiliary hypotheses
Hard core = unshakable beliefs of practitioners Negative heuristic “Don't change the Hard Core!” E.g. “DNA turns to RNA turns to protein” To be defended against falsification
Aux hypotheses = beliefs that can be revised E.g. “Gene XYZ regulates pathway ABC” Protective belt around hard core
Lakatos' answer to Kuhn's paradigmProgressive vs. degenerate
Progressive: growing, new predictions, techniques, novel predictions!
Degenerate: not growing, or no new facts in protective belt, ad hoc changes!
Larry LaudanAn American
Less colorful pass than Central EuropeansResearch traditions
Emphasizes problems solved over the theories of Lakatos' research programmes
All research traditions face 2 kinds of problems Empirical (Kuhnian anomalies) Conceptual (consistency with self or allied fields)
Rational acceptance/rejection of res. traditions Accept res. tradition that solved most problems Pursue res. tradition that's solving them at
fastest rate No notion of:
Cumulative progress (solved problems -> unsolved) Novel prediction = good, ad hoc = bad
A Sociological Perspective
Sociologists have studied scientists Toronto high-energy physics Dept. Conclusion “Run as a benign dictatorship” The “Dictatorship”
Older (read tenured) profs ran the committees of the department, were the bosses
The “benign” Younger (read untenured) profs knew the older guys
ran it and wanted them to! Younger profs wanted to concentrate on research
An extreme Sociological Perspective
Do the things talked about by these physicists really exist? Epistemological constructivism
Maybe yes, maybe no. Scientists acting in own interest (More papers!)
Ontological constructivism They are just socially-constructed things, like poems
or judicial system laws Hey is there a problem here with sociology too?
Philosophy and Self-consistency:
Philosophers make a living looking for inconsistencies in the other guys thinking Logical empiricists
Is language that devoid of metaphysics? Is reduction possible?
Kuhn Is there really no notion of progress?
Lakatos Is the “research programme” view itself a progressive
view of science? Laudan
What exactly is a research tradition and how do you know how many problems it has solved?
Sociologists Isn't your work just socially-constructed too?
Model-base philosophies of Ronald Giere
Wants to get away from “laws” Are not necessarily true Newton's Laws + Gravity assume no other
gravitational fields aroundScientific model:
Restrict generalization to some portion of “reality”
Only some objects Only some of their attributes
Compare behavior of abstract system (“model”) to allowed aspects of “reality”
Model only intended to model aspect of subset of reality
Example: Harmonic oscillator
Reality: Universe has many
things, including this spring
Model Equation: F = -kx Limited generaliztn:
k akin to spring's stiffness
x akin to mass's offset from equilibrium
Differences Between CSD and Philosophy of Science
1. Since Logical Empiricism, Philosophers of Science are interested in
What knowledge looks like If progress is being made How “real” the terms used are
2. Computer Scientists, however, are interested in writing systems that can manipulate
What shall we conclude from all of this?
1.Write systems! Do science! If scientists like our programs they will follow After the scientists follow, the philosophers
begrudingly and belatedly will This has happened once before in mathematics Proof for 4 color mapping problem done by
computer, people at first refused to call this “mathematics”
2.Philosophers of science will call what we do
“Logical Empiricism” because they are too arrogant to listen to the differences
Philosophical Issues (1)Realism vs. Instrumentalism
As real or instrumental as the scientist(s) wantReal:
Can point to simulated things and enumerate interactions
Examples: Simulation of planets
Instrumental: Imperfect simulations for lack of:
Memory Time Knowledge of initial state
Examples: protein folding in a vacuum Simulations of US/World economy
Philosophical Issues (2)
Language Use the language the scientist(s) give you Construct new terms from it
Probably definitional “New term” = “These relationships among old terms” Constructive abduction
Might have added expressive power if given “primitives” from which can express set of increasingly more powerful ideas
More have even more ideas if can define one's own set of primitives
HOW!?
Philosophical Issues (3)
Reductionism If its what the scientists want Often task is constructive
Build up how world looks from these primitives Subset of larger, reductionist task:
Try different sets of primitives to build up how world looks
Sometimes no “reductionism” in physics sense How would you tell a computer about evolutionary
biology?
Philosophical Issues (4)
Progress Of course want progress in the normal science
conceptualization Which do scientists want more?
Empirically justifying as many claims as possible (Logical Empiricists)
Making model that falsifiable, but not yet falsified (Popper)
Increasing body of theory (Lakatos) Increasing solved number of problems (Laudan)
Philosophical Issues (5)
Revolutions Better solve the “re-assemble the world from
your own primitives” problem first Don't worry too much about?
Most scientists, most of time, do Normal Science By working within given search space (primitives) can
reduce search space for answer User would want to steal credit away from program
anyway Ability to do thought experiments?
How would you even tell a computer about thought experiments?