With such a high volume of information in our daily lives, what are useful principles or heuristics for determining how much, or which kinds of, investigation are required for making an evaluation of a given claim?

I want to learn about how to decide how justified we should be making our beliefs about claims. The question stems from the problem that I don't have the resources to evaluate all the claims made to me with the most rigorous methods available. Although I would agree that principles like the burden of proof and provisionalism make this problem easier, we still need to decide if we spend five minutes or the rest of our lives working on investigating certain claims. I'm also fine saying I don't know, but I may also be okay saying X is caused by Y, at least to the extend that [cited experts] can agree.

2 Answers 2


Another aspect on top of the existing answer is to consider the cost of being wrong.

If you tell me adding more salt to a recipe will improve the taste, and you are wrong, I will have one substandard meal, and I will know better next time. I am willing to provisionally accept your advice, without even checking if you are an expert or have done randomised, controlled, double-blinded trials on the recipe.

If you tell me that homeopathic vaccines work against malaria when travelling, I could get horribly sick and die. I need additional evidence, and it is worth further investigation.


This is a broad question. How justified should your belief in a claim be? Your belief should be in proportion to the evidence. Here are some heuristics for evaluating the evidence given certain types of claims.

For breaking news, I find On the Media's "Breaking News Consumer Handbook" useful.

For fact-based claims (did X happen?, did X say Y?, etc.), following the standards of good journalism will help lead you to the correct answer, or at least avoid incorrect answers. NPR's ethics handbook gives a set of tactics. Here are just a few:

  • seek diverse perspectives
  • double-check numbers and the way they're portrayed
  • be skeptical of images; start with the presumption that they are not authentic
  • identify sources for each fact you are relying on

For more nuanced claims that involve scientific uncertainty (e.g. does X cause Y?), this is a difficult task to do right. You have to familiarize yourself with the large body of research on a topic. Give more weight to more rigorous methods and complete reviews. Follow the evidence, and be willing to accept uncertainty in your conclusion. As in all exercises of skepticism, even when think you've arrived at a well supported conclusion, you need to be open to change if presented with new evidence.

Be on guard against pseudoscience. TEDx/TED distributed a letter to TEDx organizers with heuristics to help them identify pseudoscience. Here are a few:

  • A mark of good science: It makes claims that can be tested and verified
  • A mark of bad science: Is not based on experiments that can be reproduced by others
  • Red flag behaviour: Provides data that takes the form of anecdotes, testimonials and/or studies of only one person
  • I agree, the question is very broad! I strongly agree with the advice you give in your answer, but my question was not 'how do we know' what we believe.
    – user25796
    Commented Apr 12, 2015 at 19:48

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