The document discusses various positions regarding scientific realism and antirealism. It presents an example from the 19th century of a scientist, Jones, developing a theory that an unobservable microbe called a "crobe" is responsible for transmitting disease in the same way that lice transmit diseases. While the theory is empirically successful, some argue we cannot know if crobes truly exist. The document explores arguments for scientific realism, antirealism, and a middle position of "entity realism," discussing what types of claims we can and cannot make regarding observable versus unobservable entities based on empirical evidence and scientific theories.

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Goal of science:
develop good theories of
the world.

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Goal of science:
develop good theories of
the world.
What makes a theory good?

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Science aims for literally
true theories.
Science aims for empirically
adequate theories.
Scientific Realism:
Scientific Antirealism:
Realism vs. Antirealism

5. Empirically adequate =
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Making true claims about
all the observables
(but claims about
unobservables might be
false)

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Is an aim of science
literally true theories?
Grover Maxwell: YES!
(Jones’ theory of disease)

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Disease spread by:
• bodily contact with sick person
• contact with items handled by
sick person
Observations:
Another phenomenon with
same pattern of spread: LICE

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Disease spread by “crobes”
transmitted in the same
ways lice are transmitted.
• Crobes too small to be seen.
• Halt spread of disease by
halting spread of crobes.
Jones’ conjecture

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• Predicts who will get sick.
• Suggests ways to stop spread
of disease (“disinfection”).
Theory works!
Should we believe in crobes?

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Maxwell:
No principled line we could
draw between observable
and theoretical entities.
Nothing disreputable
about crobes!

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NOT a problem of
observable vs.
theoretical entities.
Problems with Maxwell
Rather, observable vs.
unobservable.

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Rather, no data to
determine whether they
exist or not.
Antirealist doesn’t need
to say unobservable
entities don’t exist.
Problems with Maxwell

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Argument from success of
theory to existence of
crobes is logically flawed!
Problems with Maxwell

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So, crobes exist!
1. If there are crobes, and if
crobes cause disease, then
taking steps X to stop their
spread will reduce the
incidence of disease.
2. Taking steps X is followed
by a reduction in the
incidence of disease.

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So, my battery is dead.
1. If my battery is dead,
then my car won’t start.
2. My car won’t start.
Bad logic!
(“Affirming the consequent”)

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Can only get empirical
evidence about observables,
not unobservables.
van Fraassen’s
antirealism:
Constructive empiricism

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van Fraassen’s
antirealism:
Constructive empiricism
If I accept a theory, I believe
the claims it makes about
observables are true.
Claims theory makes about
unobservables could be false.

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Detectable with
unaided senses.
Observable:
• some observables may not
have been observed.
• some things would be
observable if they existed.

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Not detectable with
unaided senses.
Why aren’t crobes
observable?
What you see:
consequences of arrangement
of instrument + sample

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Duhem:
Observations with
instruments assume theory
of the measuring device
arrangement of
instrument + sample
observables
(seen through
lens)
unobservables
(causing what
is seen)
?

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Accepting a theory
Realist:
I believe all the claims the
theory makes are true.
Antirealist:
I believe the claims the
theory makes makes about
observables are true.

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Hacking’s middle
position:
“Entity Realism”:
I believe all the entities the
theory identifies really exist,
but some of the claims the
theory makes about them
may be false.

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Hacking:
Microscopes tell us
something is there, but may
not show us just what that
something is like.

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What a microscope gives:
Map of the interaction
between specimen and
imaging radiation.

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Features vs. artefacts:
Features observed from sample
using different types of radiation
due to real features
of sample
Features observed from one type of
radiation different using many
different samples
due to instrument

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Entity Realism:
We can believe that what we see
with the microscope is caused by
really existing entities.
Why? Because we can manipulate
those entities!
Chiharas’ mites

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Hard-core antirealist:
• Claims the mites exists
(they’re observable).
• Can’t know whether the
mites have legs or not!
• Can’t explain changes in
movement in terms of leg-
removal!

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What counts as a good
explanation anyway?
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