Only humans require a concept such as CERTAINTY--not an observed or unobserved system. A system is what it is.
Math has uncertainty. It's called probability. Humans go looking for certainty, yes. They want a definite answer. But often times when they follow the math down the rabbit hole, the answers are probabilities. The math shows that definitive certain answers to some questions are not possible in this universe.
QM is very hard to grasp for logical people. I'm a logical person, and you are too, Terry. There were several occasions I was just completely stumped in truly understanding a concept because I was looking for a classical analog to compare the concept to. Sometimes (most times) there are none. Many of the predictions pointed to by the math do not make any logical sense whatsoever. But these predictions are being backed up by experiment and being used in modern technology.
The point is, if you try to understand QM by using the logic of things we see and experience on an everyday basis, you are doomed to fail. The logic leads to predictions and understanding that are contrary to the way QM works.