From what I understand, the Heisenberg Uncertainty Principle means that we can never know the position and velocity of a particle at the same time, as the measurement of one necessarily affects the measurement of the other. Great. I understand that theory, and it makes perfect sense. But what I can't understand is why this principle is used to define degenerate states, the inability of two electrons to occupy the same space at the same time, and other exclusive properties? As I see it, the principle is a problem with measurement. OUR measurement. Or the limitations of our measuring strategies. But just because we can't measure something doesn't mean it can't exist, can it? Just because we can't measure position and velocity together doesn't mean the particle doesn't have both of these at the same time. Why does the fact that we can't measure two variables simultaneously mean that particles can't occupy the same space, measurable or not? How does this all expand to electron degeneracy?