Not knowing something is a much more stable experience than knowing something. You can build a lot on what you don't know - you can trust it. Sometimes however, all the things we think we don't know might be a consequence of thinking we know other things. For example, feeling anxious about there being no God, or about not knowing if there is one, sort of assumes that anxiety will change things, or that anxiety will help in the search for answers. Anxiety 'might' help (in so far as it subjects itself to critical scrutiny), but we don't actually know this - although the mere presence of anxiety suggests that at some basic level we think we do.When you are absolutely convinced that you no longer don't know, when you are at the point whereby you could wager your life or a loved one's life on the premise that you no longer don't know, then you probably do know. You can only be absolutely convinced that you no longer don't know when you have subjected everything to immense scrutiny via logical and scientific analysis. Believing that instinct, gut feelings or one's own subjective experience is a good enough basis for knowledge is sort of like saying it's not worth the hard work. This may be linked to the perceived value of getting it wrong, or right.Anyway, back to the question. One way of knowing that you don't know is the detection of incoherence in your belief system. E.g., believing all swans are white while also believing some swans are black suggests that person doesn't really know what colour swans are. Being able to believe two things that are inconsistent with each other is a particularly human ability, and many develop their skill at tolerating this 'itch' for most of their lives. The main reason people learn to tolerate this is because they believe things not out of respect for the truth, but because they want to feel better about something, often themselves or the nature of the world they / we are thrown into.Sorry for long comment. I'm sure there are many other ways to know what we don't know. Deep skepticism about many things is best avoided by upping the stakes and asking whether not being sure about something would actually lead to any discernible shift in one's practical life (I may have good reason to doubt objects exist outside my own mind, but I'm sure as hell not going to step out in front of a car to test the hypothesis).Paul
"One way of knowing that you don't know is the detection of incoherence in your belief system."Agreed - I think I'm proposing that it might be hard to find any belief system that doesn't contain any incoherence.