1. How do I know whether there are relevant but unknown facts?
The short answer is you can know with considerable effort, there may be or there may not be ‘unknown facts’ but from the persepective of your consciousness, the statement is arbitrary. It seems like you are looking for something I would call Omniscient Certainty. This question is similar to one I raise in the ‘universe’ thread. Which states that just because we cannot measure something accurately does not mean that it is unbounded or does not possess finite limits (e.g.- Uncertainty principle, universe, etc.). The problem is with the measurement techniques, not reality. In relation to your question, I believe a similar problem exist…
I think that new terms need to be defined in this area. I use the following…
There are:
Things that are unknown to all men yet exist for man to discover. This must be logically possible or new knowledge could not be discovered by man. To claim that this does not exist invalidates knowledge (or claims we know it all). This needs a word and a more desciptive definition. We could never determine how much of this exists, only that it does exist…
Things that are known to some/all men by a rational process. This would be knowledge.
When you speak of your question: How do I know whether there are relevant but unknown facts?
Without strict interpretation, I read it as, you meant:
How do I know if there is something unknown to me, yet known to others and with these others I have no reasonable way of getting in contact with them in a timely manner, to discover all the relevant information, before I make a decision? (Correct me if this is not your question)
My answer would be given enough time you could come to know all the facts, but would this be timely to the descision making process and would the effort spent be worth it. The claim is arbitrary and arbitrary claims are rejected because they form a feedback loop in the brain, which if given serious consideration would result in no action at all. You would just sit, contemplating all possible outcomes, trying to determine if you had all the information. No decision would ever be reached and more than likely the opportunity window to make that decision would pass while you are contemplating it. Arbitrary claims are rejected for thought efficiency…