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:

• A high DQ means the benefits are significant compared to the risks

BenefitsDQ

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 thatasbestos workers were suffering a large number of lung-related issues

• Since that time, when asbestos is found in buildings, it is typicallyremoved

• 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-04-01-2012) about claims of the existence of an animal called a skunk ape in Florida. One could make two claims:

1. The skunk ape exists OR

2. 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 LogicLogic – 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 self-deception 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