what do you think:
T + N
to deal with
S + F
reality forces everyone to deal with a complete variety of input
but as humans we have to differentiate and focus only on certain things
So we specialize somewhat.
An LII has T + N at his disposal: his primary and secondary weapons or instruments, etc..
But S + F are his dark sides.
He must use T with secondary N to deal with S+F, so as to have a sense of balance on his own. Obviously from other people, who specialize in S or F somehow, them using their strong instruments is beneficial, etc etc.
but for whatever reason thinking of things in that way made a whole lot of sense.