A  ¹⁹ They went out from us,

B  but they were not of us; for

C  if they had been of us, they would have continued with us;

A’  but they went out from us that they might be made manifest,

B’  that none of them were of us.

A:  Antichrists went out from us.  
B:  They were not really of us. Their faith was not genuine.
C: If their faith were truly genuine, they would have continued in fellowship.