WHAT I BELIEVEand, More Importantly, What I Don’t

What should I look for? Plausibility Falsifiability Evidence Sound Reasoning

Logical Fallacies Appeal to Nature

Claiming that since a thing is natural, it is therefore desirable or good.

Claiming that unnatural things are bad.A subset of Hume’s is-ought problem.

Example:“Genetic engineering is unnatural, so you

should eat only organic food.”

Logical Fallacies Affirming the Consequent

A converse error which assumes that the premises of a condition are true if the conclusion is true.

Example:“If it is raining, the sidewalk is wet. Since the

sidewalk is wet, it must be raining.”

Logical Fallacies Fallacy of the Perfect Solution

Claiming that a solution to a problem ought to be rejected because it is imperfect or will not solve all instances of the problem.

Example:“You shouldn’t use chemotherapy to treat

your cancer, because the therapy is toxic and some people die even after being treated.”

Logical Fallacies Straw Man

Mischaracterising an opponent’s position to make it easier to attack.

This is very popular.

Example:“If evolution were true, we’d see cats giving

birth to dogs. Since we don’t, evolution is false!”

Logical Fallacies Begging the Question

Also called circular reasoning.Demonstrating that a conclusion is true by

means of premises that assume the conclusion is true.

Example:“God exists, because he inspired those who

wrote the Bible, and the Bible testifies to his greatness.”

Logical Fallacies Argumentum ad Hominem

Literally “to the man”.Attacking the person, rather than the

argument he or she is making.

Example:“You shouldn’t listen to what Darwin had to

say because he was a racist.”

Logical Fallacies Tu Quoque

Literally “you too”.Appealing to your opponent’s hypocrisy in

failing to act in accordance to his or her own position.

A subset of the ad hominem.

Example:“Climate change isn’t real, because Al Gore

has a huge mansion and drives a big car.”

Logical Fallacies Argumentum ad Populum

Literally “to the people”.Arguing that a proposition is true on the

basis that many (or most) believe it to be true.

Example:“200,000 Canadians can’t be wrong! Q-Ray.

Find out what they know!”

Logical Fallacies Argumentum ad Consequentiam

Literally “to the consequences”.Argues that a proposition is true or false

based upon the whether accepting the proposition leads to desirable or undesirable consequences.

Example:“If God did not exist, life would have no

ultimate meaning.”

Confirmation Bias Our propensity to:

favour information that confirms positions that we already hold;

ignore evidence contrary to our own opinion. Often results in one-sided hypothesis

testing.

Selective Recall A subset of confirmation bias. Our propensity to remember the hits and

forget the misses. Relied upon by psychics and snake-oil

salesmen.

Inattentional Blindness The inability to perceive things that are

in plain sight as a result of distraction or focus elsewhere.

Change Blindness Failure to detect major changes in a

scene due to visual disruption (saccade, obstruction, etc.).

Falsifiability The logical possibility that a proposition

could be shown to be false. This is a very important principle in

science and philosophy. Falsifiable does not mean false. Only one of these statements is

falsifiable:“All humans live forever.”“No human lives forever.”

Falsifiability Let’s compare these statements:

“I have a teapot in my home.”“Between the Earth and Mars there is a

china teapot revolving about the sun in an elliptical orbit.”

Falsifiability What about these two statements?

“The gods abide at the summit of Mount Olympus.”

“God dwells extradimensionally, outside of space and time, and cannot be observed save by His direct permission.”

Jesus is Magic Can the “God Question” be addressed

by skepticism? Let’s check our work:

PlausibilityFalsifiabilityEvidenceSound Reasoning

The Burden of Proof Two possible default positions:

believe every proposition until proven false;withhold belief until propositions are proven

true. Given the proposition, “There is a dead

body in the trunk of my car,” which works better? Do you assume that’s true until proven otherwise?

The Burden of Proof Main problem with believing a

proposition until it’s proven false:It is logically inconsistent.

Example:Proposition 1: “Leprechauns place a pot of

gold at the end of every rainbow.”Proposition 2: “Leprechauns do not exist.”

With no evidence either way, you are forced to accept both propositions.

The Burden of Proof If you make an assertion, it is your

responsibility to provide evidence. It is common practice to shift the burden

of proof:“Prove to me that God doesn’t exist!”

Story Time! The Celebrations Encounter The Mansion on Wellington Crescent The Valour Road Mystery

Story Time! When I ask, “Do you believe me?” what

does that mean? Let’s check our work:

PlausibilityFalsifiabilityEvidenceSound Reasoning

Plausibility Questions:

How do the spirit and brain communicate?Doesn’t the brain make the spirit redundant?How could a spirit perceive the world?How could a spirit affect the world?Why isn’t Ghost Carl Sagan still contributing

to scientific research and public outreach efforts?

Why Skepticism? What’s the harm in believing?

Go to www.whatstheharm.net.They’re anecdotes. But they’re good

anecdotes. We can all be duped. Skepticism isn’t a cure. It’s more like a

vaccine. It doesn’t work for everyone, but there’s hope that one day we can achieve herd immunity.

It is easy for anyone to be overwhelmed by an organized campaign of misinformation. I know very bright people who were blown away by Loose Change when they first saw it. I know otherwise intelligent people who just cannot handle the systematic lies and distortions of the creationists – they don’t have the background and the volumes of information it would take to tackle each false claim and logical fallacy.

The same is true of the alternative medicine and anti-vaccine movement – they have a highly developed package of propaganda, misinformation, and subtle distortions – wrapped in a feel-good and empowering philosophy, that can easily overwhelm even an intelligent person.

—Dr. Steven Novella

All men are fools, and he who does not wish to see them must remain in his chamber and break his looking-glass.

—Marquis de Sade

Advice Remember to check your work:

PlausibilityFalsifiabilityEvidenceSound Reasoning

Advice Ray Hyman's Categorical Imperitive:

Don't try to explain a phenomenon until you've determined that it actually exists.

Example:King Tut’s “Curse”

Advice Let no question remain unasked

because it is deemed impolite. Freedom of expression is terribly

important: this is how the best ideas rise to the top.

Advice Skepticism is not about being closed-

minded. It's about being open to having your

mind changed. It's about evaluating evidence and using

that evidence as the basis for your beliefs.

Startling Things …that I don’t believe in:

Souls and SpiritsFree WillObjectivismSolipsismPostmodernismCultural Relativism (Mostly)The “Singularity”

The Winnipeg Skeptics Meetup Page

www.meetup.com/WinnipegSkeptics

The Official Winnipeg Skeptics Blog

winnipegskeptics.wordpress.com

Startled Disbelief Blogwww.startleddisbelief.com