“There's intelligent life on other planets.” Would you accept this claim? Accept the claim as TRUE Reject the claim as FALSE SUSPEND JUDGMENT

Credibility Who can we believe? SOURCES What can we believe? CLAIMS And how confident can we be in what we believe?

Assessing Credibility There is no simple rule for assessing credibility. Assessing credibility requires judgment. Judgment depends on background knowledge. This sort of judgment is basically induction.

Assessing content of a claim b Role of personal observation Focus of attention Preparation to distinguish features Conditions of observation Expectations, beliefs, biases

Assessing content of a claim b Role of personal observation b Role of background information Initial plausibility Novelty and conflict Extent of background information

Credibility of a source b Knowledge b Ability b Motivation Education and experience both matter Physical and mental factors may both be relevant Desires and beliefs, including prejudices may work in various ways

Common Mistakes in Evaluating unsupported claims. b Arguing Backwards

Common Mistakes in Evaluating unsupported claims. b Arguing Backwards Arguing backwards is to reason that because we have an argument with a true conclusion, in premises must be true. An argument is supposed to convince us that its conclusion is true, not that its premises are true.

Common Mistakes in Evaluating unsupported claims. b Arguing Backwards Example : Your friend says, “All CEOs of computer software companies are rich. Bill Gates is a CEO of a computer software company. So Bill Gates is rich.” Since you know that Bill Gates is rich, you decide the argument is good and that all CEOs of computer software companies are rich. Analysis: This is arguing backwards. There are lots of CEOs of computer software companies that are struggling to make a living. An argument is supposed to convince us that its conclusion is true, not that its premises are true.

Common Mistakes in Evaluating unsupported claims. b Arguing Backwards b Appeal to authority

Common Mistakes in Evaluating unsupported claims. b Arguing Backwards b Appeal to authority We saw above that we can often accept a claim based on authority. But it is a bad appeal to authority to say that we should accept a claim because a particular person said it when that person is not really an authority on the subject or has motive to mislead.

Common Mistakes in Evaluating unsupported claims. b Arguing Backwards b Appeal to authority Example : What do you think of the new tax plan the President announced? It must be good, ‘ cause Dan Rather said so. Analysis : Not everything that Dan Rather says is true.

Common Mistakes in Evaluating unsupported claims. b Arguing Backwards b Appeal to authority b Mistaking the Person for the Claim

Common Mistakes in Evaluating unsupported claims. b Arguing Backwards b Appeal to authority b Mistaking the Person for the Claim Mistaking the person for the claim. You’re mistaking the person (or group) for the claim if you believe that the claim is false because of who said it. It’s often right to suspend judgment on a claim if you don’t consider the person who’s making the claim to be a reputable authority on the subject. But saying that the claim is actually false because of who said it is a mistake in reasoning.

Common Mistakes in Evaluating unsupported claims. b Arguing Backwards b Appeal to authority b Mistaking the person for the claim Example : I don’t believe the tax cut will benefit the poorest in our society. That’s just another lie our senator said. Analysis : This is mistaking the person for the claim. Politicians don’t lie all the time. There’s no shortcut for reading and reasoning about a claim in evaluating whether to accept it.

Common Mistakes in Evaluating unsupported claims. b Arguing Backwards b Appeal to authority b Mistaking the person for the claim b Appeal to common belief

Common Mistakes in Evaluating unsupported claims. b Arguing Backwards b Appeal to authority b Mistaking the person for the claim b Appeal to common belief An appeal to common belief is to accept a claim as true because a lot of other people believe it. Typically, such reasoning is a bad appeal to authority.

Common Mistakes in Evaluating unsupported claims. b Arguing Backwards b Appeal to authority b Mistaking the person for the claim b Appeal to common belief Example : You go to England and find that everyone there is driving on the left-hand side of the road. You conclude that you should, too. Analysis : This is a good reasoning, since you also know that every country allows driving on just one side.