Evidence and Uncertainty

Squashed Asks: How much evidence do you need to “know” something—particularly where double blind experimentation is not a practical approach? Does direct experience work? The word of somebody trusted? Personal review of scientific journals? How do you make decisions when you don’t have all the information you would like—or when you have to rely on other people to provide the evidence?

I think we live in an uncertain universe in which we, with our limited minds, physiology, and lifespan have only limited ability to know anything with certainty. That being said, I would say that the quantity of evidence necessary to be convincing is sometimes variable, depending on the degree of certainty required. Even more important than quantity is, of course, quality of evidence, and some types of evidence are more convincing than others.

I would also like to point out that the quantity and quality of evidence necessary for something to be consider “known” or “proven” also depends heavily upon the consequences of being incorrect.

Evidence, Honesty, and the Value of Faith

What verifiable evidence supports your belief in a god? Unsubstantiated “miracles” don’t count. “I just feel it in my heart” or similar nonsense is not evidence. However, I will accept “I don’t need evidence,” as a valid answer–although it will make me think you are foolish and worry about your grasp on reality.

This is the first question from my “10 Serious Questions for Religious Believers,” and it’s a big one.

Evidence of one kind or another is the basis of all knowledge, but there is good evidence and bad evidence. At least, there is universal evidence and personally specific evidence. Universal evidence is evidence that can be seen, touched, experienced, and understood by anyone. Personally specific evidence is evidence that is only convincing to the person who claims to have that evidence. Personally specific evidence is always unverifiable and unreproducible.

Richard Dawkins, in a beautifully written letter to his daughter, names three types of bad evidence, or rather non-evidence, for believing anything: Tradition, Authority, and Revelation. Tradition encompasses the things that we believe because, well, that’s what people have “always” believed. When we believe something based on authority, we believe it because it was told to us by someone important, irrespective of whether or not the claim stands on its own merits. Lastly, revelation refers to the things we believe because we think we have supernatural insight that allows us to know something we otherwise wouldn’t be able to.