Critical Thinking Chapter Summary

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Chapter 4 – Reasons for belief and doubt
* If we care whether our beliefs are true or reliable then we must care about the reasons for accepting those beliefs * The better the reasons for acceptance, the more likely are the beliefs, or statements to be true * Inadequate reasons, no reasons or fake reasons should lead us to doubt a statement * When two claims conflict they simply cannot both be true * If a new claim conflicts with other claims we have good reason to accept, we have good grounds for doubting the new claim * Eg. Its common knowledge that smoking causes cancer

* Neera: i just read that smoking doesn’t cause cancer * With conflicting claims you are not justified in believing either one of them until you resolve the conflict ( in some cases resolving the conflict wont take long) * Background information – the large collection of very well supported beliefs that we all rely on to inform our actions and choices. It consists of basic facts about everyday things, beliefs based on very good evidence (including ur own personal observations and excellent authority) and justified claims that we would regard as ‘common sense’ or ‘common knowledge’. * If a claim conflicts with our background info, we have good reasons to doubt it * The more background info a claim conflicts with the more reason we have to doubt it * Facts about everyday things

* The sky is blue
* Beliefs based on very good evidence
* Cigarettes aren’t good for u
* Justified claims that we would regard as common sense or common knowledge * You’ll do better on a quiz if u study
* Most nova scotians are of European heritage
* Some babies can bench press a 500 lbs weight – you are not going to be able to accept this claim very easily because it conflicts with an enormous number of ur background beliefs. Including beliefs about physiology, gravity and weightlifting * So if a claim conflicts with our background info, we have good reason to doubt it – however it is not the same as saying it is false but rather reason to explore further. * It is possible that a conflicting claim is true or some of our background info is unfounded * Common sense isn’t always right

* Many ppl believe shark attacks are common
* Flying in an airplane is dangerous
* Suvs are safer to own that smaller cars
* These are all false
* Common sense used to tell ppl the earth is flat, animals don’t feel pain etc * Therefore revise claims closely
* If no good reasons and not credible, reject it
* If strong reasons, revise our background info
* If a claim is dubious we are justified in dismissing it * We should proportion our belief to the evidence if a claim is not quite dubious but not worthy of complete acceptance * Strong evidence warrants strong belief

* Weak evidence warrants weak belief
* Our degree of belief should vary according to the evidence * The more evidence a claim has in favour, the stronger our belief in it should be * Believing shouldn’t be ur default setting – its not reasonable to believe a claim when there is no good reason for doing so * Experts and evidence

* When an unsupported claim doesn’t conflict with what we already know, we are often justified in believing it because it comes from experts * Expert – someone who is more knowledgeable in a particular subject area or field than most other are * Provide reasons for believing a claim because in the specialty area they are more likely to be right than us * If an expert makes a claim then we are generally justified in believing it even if no evidence is given so long as it doesn’t conflict badly with background knowledge and as long as theres no specific reason to doubt this expert on this occasion * They are true authorities in a specified subject

* We must rely on experts because we cant be knowledgeable...
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