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.
For example, if I want to try something new for dinner, I may go to a restaurant that I’ve never even heard of because I like the look of their signage. The fact that a restaurant has a nifty-looking sign has almost nothing to do with the quality of their food, and is a pretty poor reason for any decision-making process. However, the worst-case-scenario consequences of making a poor decision in my choice of restaurant (out the price of a meal that I didn’t enjoy) aren’t so bad.
Of course, it’s possible that I have tried restaurants in a similarly random manner in the past and had good results. This would increase my confidence in my decision, but is not necessarily an indication that restaurants with signs that I like also have good food. Unless I had experimented extensively and standardized my methodology, it’s as likely as not that I’ve just been lucky to have not gotten food poisoning.
In any case, I don’t need to “know” that my method of picking restaurants is valid or if it can be scientifically proven, therefore the burden of evidence required for me to keep picking restaurants like this isn’t very high.
If, however, I were dealing with a more important decision, I may need much more evidence to be convinced. I would never, for instance, pick a mutual fund to invest in like I might pick a restaurant. I would want to see numbers, history, projections and so on before deciding whether or not this was a wise investment. I wouldn’t make such a decision on a hunch.
When it comes to something like religion, it’s entirely possible (if believers are correct) that there are very serious consequences for believing the wrong things. I have religious acquaintances who are not shy in saying that they think I am doomed to an eternity of fiery torment in hell because I am an atheist. So, you can imagine that I have a very high standard indeed for evidence in regards to religion and my lack thereof. Otherwise, I may just have to accept Pascal’s Wager and be content.
The short explanation of a very long story of how I became an atheist, then a deist, a panentheist, then a Christian, and then an atheist again is that in all my experience, in all my reading, in all that I have learned in my life so far, I see no evidence in favor of the existence of any god at all, much less any of the particular gods that humanity has dreamt up so far. As far as “knowing”? Well, I don’t “know” if “knowing” means “absolute certainty,” but I would say that I am as certain as it is possible to be.
Finally, when it comes to making decisions when I don’t have all the information I might need or desire? Well, I suppose I do the same thing everyone does. I weigh risks and costs against benefits and possible outcomes, make the best guess I can, and hope I haven’t screwed up. If I do screw up, then I can be content knowing that I made the best possible decision based on the information that I had at the time.