“The Demarcation Problem”
(Science and pseudo-science)
Case one: Geocentrism (an earth-centered universe) vs.
Heliocentrism (a sun centered universe).
“The Demarcation Problem”
(Science and pseudo-science)
Case one: Geocentrism (an earth-centered universe) vs.
Heliocentrism (a sun centered universe).
“The Demarcation Problem”
Case one: Geocentrism (an earth-centered universe) vs. Heliocentrism
(a sun centered universe).
Was geocentrism a scientific hypothesis?
How much of it was based on theology or appeals to ancient
authorities (such as Aristotle), rather than on empirical
evidence and/or scientific reasoning?
Was heliocentrism a scientific hypothesis?
How could it be if it so obviously clashed with our experience?
Where is the wind? Why don’t we feel the earth’s motion?
How does a telescope work? How do we know what Galileo
claimed to see (e.g., that Jupiter has moons) weren’t just
artifacts produced by his telescope?
Popper: “Falsifiability is the criterion”
Why reject verifiability?
 By then (for reasons we will study shortly),
scientists and philosophers recognized that no
empirical theory could ever be proven.
 This seemed to take any degree of certainty off the
table
 Moreover, according to Popper, “verifications” or
confirmations of a theory were, in many cases, all
too easy to come by.

Popper: “Falsifiability is the criterion”
By then (for reasons we will study shortly),
scientists and philosophers recognized that no
empirical theory could ever be proven.
 But Popper has logic on his side; for while no
empirical theory can be proven, any (genuinely)
empirical theory can be disproven and, at least in
principle, by just one failed experiment or
prediction.

The logic of confirmation vs. the logic of
falsification
If H, then I
2. I
-----------------H
Logic of confirmation:
Affirming the consequent
Deductively invalid
1.
If H, then I
2. Not I
-----------------Not H
Logic of falsification
Modus Tollens
Deductively valid.
1.
Popper: “Falsifiability is the criterion”
In 1919, Popper compares 4 then popular and
much discussed theories: Relativity, Marxism,
Freudianism, and Adlerian Psychology
 Although the last three might contain important
truths or insights, and although they are said to
enjoy extensive confirmations (supporting
observations and “experiments”), they turn out not
to be scientific, according the Popper.
 Although it was unclear at the time whether
Einstein’s theory was true, it turns out to be
scientific on Popper’s view.

Eddington’s experiment
Einstein’s theories predicted that light, like
material objects, is subject to the gravitational
“pull” of large objects
 Hypothesis: light traveling from a star that is
located “behind” the sun from the perspective of
the Earth should bend as it passes the sun
 A bold hypothesis and one that would take years
to carry out. Scientists had to wait for a solar
eclipse so that a star’s light would be visible

Eddington’s experiment

A reconstruction of what Eddington’s photographs
demonstrated:
Eddington’s experiment
A bold hypothesis and one that would take years
to carry out. Scientists had to wait for a solar
eclipse so that a star’s light would be visible
 But it was not its confirmation that struck Popper,
but its falsifiability and boldness: even before
Eddington’s experiment confirmed it, scientists
knew what would, in principle, falsify the
hypothesis: namely, not observing the bending of
the light traveling from the star toward Earth.

Falsifiability
The criterion used to make these judgments and to
be generalized:
 Every genuinely scientific theory is a prohibition.
It forbids certain things to happen.
 A theory that is not falsifiable (refutable) by any
conceivable event is not scientific.
 Confirmations should only count as supporting a
theory if, like that of Relativity, they involve risky
and bold predictions.

Falsifiability
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Using the criterion to judge Marxism, Freudianism, and
Adlerian Psychology as examples of pseudo-science
The problems with Freudian and Adlerian psycyhology:
Each is compatible with every possible state of affairs.
Each contains within it the means to explain conflicting
results (e.g., whether an adult jumps into water to save a
drowning child or does not jump in – explanation “his or
her feelings of inadequacy”)
The “unconscious” of Freudian theory undercuts any
individual’s claim not to experience what Freud predicts
every male, or every female, experiences.
Falsifiability
Marxism is rendered pseudo-scientific not
because the original theory was not falsifiable.
 Marx and Engel’s claims about upcoming
proletariat revolutions in capitalist societies were
falsifiable, and in most cases, falsified.
 But advocates of Marxism, in efforts to save the
theory from the falsifications, introduce Ad hoc
hypotheses to save it.
 Ad hoc: From the Latin “for this purpose” (in this
case, saving the theory…)

Falsifiability
Ad hoc hypotheses and Marxism
 According to Marxism, each society has an
“ideology” – a guiding set of ideas – that informs
its political and economic theories and institutions
 Ideologies function to make the present political
and economic status quo look natural
 So, workers (members of the proletariat) don’t
recognize that capitalism exploits them and have
to be taught to see through the ideology that their
economic system is a “meritocracy” with
unlimited possibilities to succeed.

Falsifiability
When the many revolutions Marx and Engels
predicted did not occur, later advocates of the
theory pointed to the capitalist ideology as the
culprit: workers couldn’t see through it and
recognize the truth. Hence, few revolutions.
 Note that this is a different kind of case from
Freudian and Adlerian psychology: it’s not the
theory that is unfalsifiable, it’s the attitude of its
advocates and their willingness to propose Ad hoc
hypotheses to save it from falsification

Things we will later consider…
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The difference between a theory actually being
unfalsifiable, by its nature or structure, and a theory’s
advocates resorting to ad hoc hypotheses to save it.
Isn’t it possible that a genuinely scientific theory will
be confirmed repeatedly and no counter-examples
encountered?
The “in principle” caveat is important. “There is a
little red school house on the dark side of Jupiter” is
silly but falsifiable in principle.
How easy or straightforward is it to identify added
hypotheses that ARE ad hoc, but added hypotheses
that are NOT ad hoc (i.e., are defensible)
The Elegant Universe: preview
The two pillars of contemporary physics –
Relativity and Quantum mechanics – are (it
appears) incompatible.
 Relativity theory concerns very large objects
(galaxies, starts, and the like)
 Quantum mechanics concerns very small objects
(atoms and subatomic particles)
 They yield different laws.
 Unification – “a theory of everything” is for many
physicists the Holy Grail.

The Elegant Universe: preview
String Theory is seen by some physicists as
precisely the theory that will unite Relativity and
Quantum mechanics – it is (it will turn out to be)
the theory of everything.
 It posits that everything, including Lederman’s
quarks and leptons, is made of tiny, vibrating
strands of energy (they’re called strings)
 It has led to some strange predictions: parallel
universes and 11 (yes, 11!) dimensions, among
other things.

The Elegant Universe: preview
Note how string theory, like particle physics,
quantum theory, the Greeks of Miletus, and
Democritus, assumes there is one stuff out of which
everything is made.
 Strings are, by their nature, unobservable (and,
indeed, there are no technologies able to indirectly
observe their effects – although some hope LHC
will help here)
 Note the primary reasons physicists who are not
String Theorists reject its status as “scientific”!

The Elegant Universe: preview
Some of the players:
 Brian Greene, narrator and author of the book of
the same title. Professor of physics at Columbia
University. An advocate of String Theory…
 Sheldon Glashow, Professor of Physics, Harvard,
Noble Prize in Physics, author of the “Credo” we
read earlier.
 Steven Weinberg, Professor of Physics, University
of Texas, Austin. Shared the Noble Prize with
Glashow for their construction of “The Standard
Model” in physics.
