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      CS 99D - The structure of scientific revolutions, January 23, 2001

				  Marc Levoy
			      Stanford University
				   (c) 2001

		      (with corrections, March 14, 2003)

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			     *** Introduction ***

Why study this?
	o representative of all intellectual revolutions
	o training for life

The impact of Kuhn's work:
	o change in historial methodology - rereading of "who knew what when"
	in the context of the prevalent paradigm

	o looking for changes in paradigms in other disciplines
		-> Huntington's The Clash of Civilizations

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		  *** Definition of a scientific paradigm ***

What is a science?  A discipline in which, at least during "normal" periods:
	o progress can be made -
		knowledge is cumulative
	o solves problems -
		"The unit of scientific achievement is the solved problem."
		"Novelty for its own sake is not a desideratum in the sciences
		 as it is in so many other creative fields."
			- p. 169

What is a scientific paradigm?
	o system of definitions (axioms, beliefs)
	o set of theories based on those definitions
	o criteria for proof of these theories
	o experimental methodologies for obtaining these proofs
	o collection of instruments for performing these experiments

	o a "network of commitments"
	o a "scientific tradition"
		-> Ptolemaic astronomy
		-> Newtonian dynamics

	o the need for paradigms
		"Truth emerges more readily from error than from confusion."
			-Francis Bacon, quoted on p. 18

		"There is no such thing as research in the absence of any
		paradigm.  To reject one paradigm without simultaneously
		subtituting another is to reject science itself." - p. 79

Pre-paradigmatic science:
	o competing schools of thought
		-> extromissionist / intromissionist theories of vision
	o no common body of belief, nothing people can agree on
		-> Descartes believing he must clear his mind first
	o no ability to distinguish relevant from irrelevant facts

		"Being able to take no common body of belief for granted, each
		writer...felt forced to build his field anew from its
		foundations." - p. 13

Paradigmatic science:
	o creative work is addressed to and evaluated by community members -
		specialists
	o students are trained by secondary works (textbooks),
		not primary works ("classics")

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	      *** The four stages of a scientific revolution ***

1. Normal science
	o mopping up by gathering facts that:
		o support a paradigm, refine constants
			-> Michelson refining the speed of light
			   assumes certain things about the nature of light
			   (between Mt. Wilson and Lookout Mtn. near Mt. Baldy)
		o verify predictions of the paradigm
			-> Gravity Probe B verifying Einstein's predictions
		o "articulate the paradigm" - define its applicability
			-> Can we speed up evolution by irradiating animals?

	o puzzle solving
		o problems that are assumed to have a solution (p. 37)
		o what engages most scientists throughout their careers
		o by working within a paradigm, things may be overlooked
			-> CG research using a workstation and mouse

	o the difference between paradigms and rules for research (p. 44)
		o scientists' rules are learned by example / apprenticeship
		o paradigms can exist without a discoverable set of rules
			-> design is taught this way
				(architectural, industrial, computer)

	o the imperfection of paradigms
		"To be accepted as a paradigm, a theory must seem better than
		its competitors, but it need not, and in fact never does,
		explain all the facts with which it can be confronted." - p. 17

2. Anomaly
		"Normal science does not aim at novelties of fact or theory
		and, when successful, finds none."  "Discovery commences with
		the awareness of anomaly." - p. 52

	o kinds of anomaly:
		o accidental discoveries
			-> Roentgen's discovery of X-rays (p. 57)
		o unexpected results
			-> Michelson and Morley's failure to detect the ether

		"Novelty ordinarily emerges only for the man who, knowing with
		precision what he should expect, is able to recognize that
		something has gone wrong." - p. 65

	o the progress of an anomaly
		1. deny it, ignore it, or mistake it
			-> others ignored fogging of their photographic plates
			-> Columbus thought he had discovered the (East) Indies
		2. explore it
			-> Roentgen spent 28 days "non-stop" in his laboratory
		3. express it in the language of the current paradigm
			-> X-rays are "a special kind of light" -Roengten
		4. conclude that it endangers the current paradigm

		o compare to the stages of mourning:
			denial, anger, resignation, acceptance

3. Crisis
	o the progress of a crisis
		1. attempts to fix existing theory, followed by
		   admittance that the current theory is busted
			-> pre-Copernican fixes to Ptolemaic astronomy
		2. proliferation of versions of a theory, followed by
		   regression to pre-paradigmatic science (no theory at all)
			->corpuscular versus wave theories of light
		3. loosening of the rules for research,
		   a switch to "extraordinary science"
			-> Kepler fitting the motion of Mars using any function
		4. emergence of new theories
			-> Darwin's random mutations selected by survival

		"Rarely is a theory dislodged by a negative attack alone...what
		is required is an alternative theory that will displace the old
		by virtue of greater theoretical power and fecundity."
		-Lindberg, p. 67

	o how to conduct extraordinary science:  (p. 87)
		1. push the old theory - test its limits
		2. magnify the breakdown - try to make it suggestive
		3. search at random
		4. invent wild theories

	o search for crucial experiments
		o experiments that will settle the battle between paradigms
			-> Newton's "experimentum crucis" with prisms

	o competition between paradigms
		o debates are typically at cross-purposes

			"The proponents of competing paradigms will often
			disagree about the list of problems that any candidate
			for paradigm must resolve."

		o practical considerations - which explains more facts?
		o aesthetic considerations - which theory is more elegant?

		o the competition is seldom "resolved"
		o the proponents of the old theory simply switch or die

			"Almost always the men who achieve these fundamental
			inventions of a new paradigm have been either very
			young or very new to the field." - p.90

	o outcomes of crisis: (p. 84)
		1. normal science proves able to handle the crisis
		2. problem set aside for future generations with better tools
		3. transition to a new paradigm, return to normal science

4. Revolution (optional)
	o why call it a "revolution"?
		o analogy between theories and governments

			"Existing institutions have ceased adequately to meet
			the problems posed by an environment."

			"Political revolutions aim to change political
			institutions in ways that those institutions themselves
			prohibit." -p. 93

		o revolutions are by definition extra-institutional

	o types of revolutions:  (optional)
		o scientific - Greek, Enlightenment
		o technological - Industrial, Electrical, Atomic, Information
		o artistic - Greeks, Renaissance, Impressionists, Moderns
		o political - Age of revolution

	o effects of revolution on old observations  (p. 126)
		o observation = senses + experience
		o there is no pure observation-language
		o revolutions effect a transformation of vision
		o hence observations must be reinterpreted after a revolution
			-> mixtures of carbon and oxygen after Dalton (p. 134)

	o effects of revolution on old facts:
		o new paradigms often include the old as a special case, i.e.
		o the old paradigm is still true in a restricted context
			-> Newton's dynamics are true if v << c  (p. 99)

	o effects of revolution on old problems:
		o new paradigm may re-open old problems
			-> Kepler's retinal image re-introduced inverted images

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	*** Scientific writing and the invisibility of revolutions ***

Current scientific writing makes revolutions invisible:

	o textbooks

		"Scientists... see its discipline's past developing linearly
		toward its present vantage."

		"Textbooks...have to be rewritten in the aftermath of each
		scientific revolution, and, once rewritten, they inevitably
		disguise...the very existence of the revolutions that produced
		them."

		"Why dignify what science's best and most persistent efforts
		have made it possible to discard?"

		o writing textbooks usually impairs rather than enhances ones'
		reputation (p. 20)

	o scientific papers

		o people don't read old papers, and much is lost:

			"There are losses as well as gains in scientific
			revolutions, and scientists tend to be peculiarly blind
			to the former."  -p. 167

		o we take from the literature of the old paradigm only what
		seems useful to the new paradigm *at the time of the
		revolution*

The importance of understanding the history of science: (my ideas)

	o Thesis #1: scientific education equips students for normal
	science, but not for the extraordinary science needed during
	paradigm crises.

	o Thesis #2: learning the history of science improves a
	student's ability to appreciate the limits of a paradigm and to
	think creatively beyond it.

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