Replied . Send me the time stamps when you get a chance . <| sep |> Isn ' t the only other bounty hunter Zam Wesell ? <| sep |> The problem here is that you ' re working with the ' ELI 5 ' version of the Pauli exclusion principle . It ' s a nice simple way of stating the Pauli exclusion principle , No identical fermions can ever be in the same state , but it isn ' t very precise . You can get confused , like in your example , Well I have one atom with an electron in this state over here and I have another atom with another electron over there in the same state , is that allowed if the 2 atoms or separated or not or what ? The more precise definition of the Pauli Exclusion Principle in the nonrelativistic context is that the wavefunction must be antisymmetric under the exchange of any two identical fermions . Mathematically , let x 1 , x 2 , . xN represent the coordinates of N independent particles . Then , there is a wavefunction for this system Psix 1 , x 2 , ., xN . There is only ever one wavefunction and it describes the entire system . Any smaller systems contained in the total system do not , stictly speaking , have their own independent wavefunctions . What other people have pointed out is that if subsystems A and B are weakly interacting then we can approximately write the total wavefunction as a product of a function that describes subsystem A times a function that describes subsystem B . Armed with this knowledge we can state the Pauli exclusion principle more precisely in a mathematical way . The Pauli principle requires that Psix 1 , . , xi , xj , . , xN Psix 1 , . , xj , xi , . , xN for xi and xj the coordinates of 2 identical Fermions . Swapping xi with xj in the wavefunction must be equivalent to multiplying the whole thing by 1 . With this statement of the principle , all this worry about whether we have 1 or 2 or 200 systems falls away . What we require is that for the wavefunction that describes the entire universe , swapping any 2 identical fermions must be equivalent to multiplying the original wavefunction by 1 . If you have the situation where the wavefunction can be written as a product of 2 approximately noninteracting factors , the same principle applies , both within each subsystem and between the two subsystems .