Read Sections 1.4 and 1.12 in the
textbook before reviewing the slides
Unit 2
•Desirability Quotient (1.4)
•Critical Thinking – the FiLCHeRS approach (1.12)
Desirability Quotient (1.4)
• Scientific advances often offer benefit but
also bring some level of risk
• Desirability quotient (DQ) is a means of
evaluating benefit and risk and is given as:
Benefits
DQ 
Risks
• A high DQ means the benefits are
significant compared to the risks
Example of DQ
•
•
•
•
Asbestos was previously used in building construction materials, particularly
for insulation around pipes as in the picture to the right
Concerns about asbestos causing mesothelioma, a form of
lung cancer, arose due to observations in the late 1970’s that
asbestos workers were suffering a large number of
lung-related issues
Since that time, when asbestos is found in buildings, it is typically
removed
Asbestos lung cancer deaths in the United States are estimated to be barely
statistically measurable
Benefits of removal
Risks of removal
Occupants not exposed to asbestos
Workers exposed to airborne
asbestos
Firefighters would not be exposed in
case of fighting a building fire
Removal may put asbestos in the air,
its most problematic form
Cost is extremely high
Example of DQ (cont.)
• The value of the DQ for asbestos abatement depends on
the situation.
• For example, in a school with asbestos pipe insulation or
flooring that is intact, the risk of removing the asbestos
with the potential of making it airborne may outweigh the
benefits of having it removed from the building
• If instead, the asbestos pipe insulation is worn and
shredded or asbestos flooring is not intact, the benefit of
getting rid of it would probably outweigh the risks
Critical Thinking (1.12)
• How do we evaluate the validity of a scientific
claim? Notice we are not talking about
whether or not the claim is true – only if it is a
valid claim based on the following criteria.
• Can use an approach with the acronym of
FiLCHeRS (Lett, James, The Skeptical
Inquirer, Volume 14.4, Fall 1990)
• A claim might be true if it passes all six
FiLCHeRS tests given on the next two slides
• If it fails any of the tests it is likely to be false
FiLCHeRS Criteria
• Falsifiability – must be possible to
conceive of evidence that proves a claim
false
• Logic – argument offered as evidence in
support of any claim must be sound
• Comprehensiveness – evidence must be
exhaustible – all evidence is considered
• Honesty – evidence evaluated without
self-deception or bias
FiLCHeRS Criteria (continued)
• Replicability – experimental evidence must
be reproducible
• Sufficiency – evidence offered in support
of a claim must be adequate to establish
the claim’s truth
FiLCHeRS Example
• Consider Critical Thinking Exercise 1.1 from page 33
of your textbook:
An alternative health practitioner claims that a nuclear
power plant releases radiation at a level so low that it
cannot be measured, but that this radiation is harmful
to the thyroid gland. He sells a thyroid extract that he
claims can prevent the problem.
• How would this claim be evaluated by FiLCHeRS?
Remember, if it fails any of the FiLCHeRs tests it is
determined to be an invalid claim and the process can
stop.
Analysis of Low-Level Radiation
There are really three claims wrapped up in this one
problem:
 a nuclear power plant emits an unmeasurable
level of radiation
 this radiation is harmful to the thyroid gland
 the thyroid extract he sells can prevent the
problem.
If a claim fails any of the FiLCHeRs tests it is
deemed to be a false claim and the process can
stop.
FiLCHeRS Test for Radiation
Problem: Falsifiability?
Are the claims falsifiable?
Consider the three claims:
– Low level emission: if it can’t be measured, it cannot be verified even if
it is present, thus it is not falsifiable. Since this claim is not falsifiable, it
is already determined to be an invalid claim.
– Harmful to thyroid: if the existence of the radiation is not verifiable,
certainly its effect on the thyroid would be impossible to determine.
Once again, since the radiation cannot be determined to be present it is
impossible to determine its effect on the thyroid gland and thus the
claim cannot be falsified. This claim is determined to be invalid.
– Thyroid extract: if the existence of the problem cannot be determined
then it will likewise be impossible to determine whether his extract can
“prevent” an unverifiable problem. This claim is determined to be
invalid.
FiLCHeRS Test for the Skunk Ape:
Falsifiability?
I read on an airline magazine
(http://www.americanwaymag.com/columnists-04-012012) about claims of the existence of an animal
called a skunk ape in Florida. One could make two
claims:
1.
2.
The skunk ape exists OR
The skunk ape does not exist.
Notice only the second claim is falsifiable – the
capture of a skunk ape would invalidate the claim –
thus it is a valid claim. It would be impossible to falsify
the first claim because not finding a skunk ape doesn’t
prove it.
FiLCHeRS Test for Logic
Logic – argument offered as evidence in
support of any claim must be sound
Consider an example from Lett’s article:
All dogs have fleas → Fido has fleas → Fido is a dog
This logical flow is invalid because other animals can
have fleas as well – Fido could be a parakeet. A
different problem:
All dogs have fleas → Fido is a dog → Fido has fleas
This statement is logical but unsound. The first
statement is not true – not all dogs have fleas.
FiLCHeRS Test for
Comprehensiveness
• Comprehensiveness – evidence must be
exhaustible – all evidence is considered
Suppose as an example that someone claims to
be clairvoyant and makes a series of predictions,
some of which are correct. To evaluate the
clairvoyant's ability, one would also have to
consider predictions that did not come to fruition.
FiLCHeRS Test for Honesty
• Honesty – evidence evaluated without selfdeception or bias
Honesty is closely related to comprehensiveness. The
question is, once all of the data is in place, is it
evaluated without favoritism to determine the
outcome of the claim. In the clairvoyant example,
leaving data out is violating the comprehensiveness
test. However, including all of the data and making
excuses for the results that do not support a claim is
an example of violating the honesty principle.
An “Everyday” example of not paying attention to
Comprehensiveness and Honesty
Washington Post, May 29, 2011
Another “Everyday” reason for us to develop our own ability to evaluate claims
Washington Post, May 29, 2011
FiLCHeRS Test for Replicability
• Replicability – experimental evidence must
be reproducible
Gerard Croiset was considered a parapsychologist
in the 1900’s and some thought he had the
ability to solve crimes. Though he had a couple
of successes in a very long career, most of his
predictions were vague and many more were
wrong. Thus, his ability to predict such things
was not replicable. One could also consider
this a violation of comprehensiveness or even
honesty – only considering select cases.
FiLCHeRS Test for Sufficiency
• Sufficiency – evidence offered in support
of a claim must be adequate to establish
the claim’s truth
The more extraordinary the claim, the more significant the
evidence must be. If you say you were abducted by
aliens, some pretty solid evidence would be needed to
support that claim.
The End