# What causes Paulis Exclusion Principle?

Currently I'm taking an astrophysics class and has now come across electron degeneracy. As far as I understand, the reason why white dwarfs and such, does not collapse, is due to this, meaning that the electrons are so close together in the core, that the Pauli exclusion principle prevents them from getting closer, even though the gravitational pressure is so high.

My question is: What force makes this possible? The Coulomb force? Is it just something you have to come to terms with, that no fermion can be in the same state, or is there actually a force that makes sure this does not happen?

• To understand Pauli's exclusion principle, I recommend Wouter's answer here: physics.stackexchange.com/questions/69241/… – jinawee Oct 10 '14 at 18:49
• It follows from the indistinguishability of similar particles (which follows directly from Heisenberg's uncertainty principle), & the spin-statistics theorem. Section 61 here might help books.google.ie/… – bolbteppa Oct 10 '14 at 22:10
• – John Rennie Oct 11 '14 at 9:30

Since electrons have spin $\frac{1}{2}$, the spin-statistics theorem tells us that they must behave like fermions.