Many times we need to be able to evaluate an unsupported claim—a claim that isn't backed by an argument. There are several critical thinking principles that can help us do this. An important one is this: If a claim conflicts with other claims we have good reason to accept, we have good grounds for doubting it. Sometimes the conflict is between a claim and your background information. Background information is the large collection of very well-supported beliefs that we rely on to inform our actions and choices. The relevant principle then is this: If a claim conflicts with our background information, we have good reason to doubt the claim.
It is not reasonable to accept a claim if there is good reason to doubt it. In the case of claims that we can neither accept nor reject outright, we should proportion our belief to the evidence.
An expert is someone who is more knowledgeable in a particular subject area than most others are. The important principle here is this: If a claim conflicts with expert opinion, we have good reason to doubt it. We must couple this principle with another one: When the experts disagree about a claim, we have good reason to doubt it. When we rely on bogus expert opinion, we commit the fallacy known as the appeal to authority.
Many claims are based on nothing more than personal experience, ours or someone else's. We can trust our personal experience—to a point. The guiding principle is this: It's reasonable to accept the evidence provided by personal experience only if there's no reason to doubt it. Some common factors that can raise such doubts are impairment (stress, injury, distraction, emotional upset, and the like), expectation, and our limited abilities in judging probabilities.
Some of the common mistakes we make in evaluating claims are resisting contrary evidence, looking for confirming evidence, and preferring available evidence. To counteract these tendencies, we need to take deliberate steps to examine critically even our most cherished claims, search for disconfirming evidence as well as confirming, and look beyond evidence that is merely the most striking or memorable.
Many of the unsupported claims we encounter are in news reports. Reporters, editors, and producers are under many pressures that can lead to biased or misleading reporting. The biggest factor is money—the drive for profits in news organizations, especially those owned by larger corporations or conglomerates. Reporters themselves can introduce inaccuracies, biases, and personal opinions. And the people who produce the news might decide not to cover certain stories (or aspects of stories), which can sometimes provide a skewed or erroneous picture of an issue or event.
The best defense against being misled by news reports is a reasonable skepticism and a critical approach that involves, among other things, looking for slanting, examining sources, checking for missing facts, and being on the lookout for false emphasis.
Advertising is another possible source of unsupported or misleading claims. We should realize that we generally have good reason to doubt advertising claims and to be wary of advertising's persuasive powers.