The two basic orientations of extraversion and introversion, first described in jung's psychological types in 1921, are redefined as practicality and principality.
For Extravered Thinking, as an example, it is a practicality that a square's area is the square of one of its sides. Ti, on the other hand, will put the Thinking function at work seeking a principle from which this particular incidence is to be deduced.
But if thinking is merely a tool and not an end in itself, then wonder, mystery, awe, indeed even the irrational, are the primary. Thus, the individual is free to form its own subjective relationship with the object -- not only in terms of liking or disliking the object, but also in the unique way one likes or dislikes it. Child-like and spontaneous, Fi indulges in fantasies around the object that come to define that emotional relationship.
"Nothing in life is to be feared, it is only to be understood." -- INTP
"I always live in a dream world." -- ISFP
Dominant Te gets a special treatment. Although the ET-J type still has Feeling as primary (Fi) and Thinking as a tool (Te), if that subjective emotional relationship with the object is downplayed even to degrees of total unconsciousness, this creates the tendency in the psyche of treating personal preferences as facts about the object. If I like it, it's not really because I like it, it is because it is likable.
However, all Fi-Te types agree that subjective experience is the principle and ultimate end, even if that means that Thinking has to suffer.
This is to be contrasted with the Ti/Fe axes, where Thinking is the ultimate end even at the expense of the subject.
Thus, for the Fe-Ti types, the world can be certain and is primary, but the subject has a big fat question mark next to it. And if determinism is scientifically valid, it is easy to see Fe-Ti types as moral nihilists. For the Fe type, this manifests itself as conscious or unconscious pessimism counterbalanced with an attitude of insincere optimism: Nothing will work but we should still try. As for the Ti type, this can manifest as others' exploitation: The game is already rigged, so why should I play by the rules?
'No, I can't really do much with Nietzsche [INTJ],' Leni Riefenstahl recalls Hitler [INFJ] telling her. 'He is more an artist than a philosopher'.
Coming to the perceiving functions, Ni/Se types regard intelligence as primary, while action comes second. This is in contrast to Si/Ne types, where intelligence is merely a practical tool but the end goal is to get to work and finish it.
For Se dominant types, unconscious Ni results in compensating with shortcuts and quick fixes to problems where only true genuine understanding can suffice.
As for Ne dominant types, overindulging the iNtuitive function where one applies their intelligence to the same problem over and over again becomes an escape of the underlying unconsciously accepted idea that intelligence is unrequired.