I have read that in certain nuclear reactions neutrons can knock neutrons out of the nucleus. I know this sounds weird but why don't the neutrons pass through one another? My understanding of why things don't pass through each other (at least for charged fermions) is electromagnetic repulsion and the Pauli Exclusion Principle. A neutron doesn't have charge so the only thing that prevents them from passing through one another is the Pauli Exclusion Principle. If two neutrons have opposite spins and other different quantum numbers, then what prevents them from passing through one another/occupying the same position in space? Is it due to the neutron substructure? Why must one knock the other one out?
*Obviously this emphasizes the particle aspect over eave aspect and this question assumes that position is known withon fairly reasonable bounds.