Ti and Fi are introverted judging functions. So they’re both focused on evaluating information internally, but they do so by widely different criteria.
With Ti, they try to get at some impersonal truth, so they suppress the passionate element of themselves in order not to have their judgment disturbed by personal likes and dislikes. Whatever impressions, events, and knowledge comes their way, they try to analyze that in an impartial way.
With Fi, they’re trying, above all else, to arrive at their own personal truth. The Fi types are very passionate, but the passion is within and it’s very hard for them to express. Even though they can be witty and quirky while speaking, it’s also as if though they can never fully communicate the sense of value and truth that they have in their heart. They can never get it entirely out into the outer world.
So frequently Fi types are very good artists and fiction writers and so on. They are ‘artistic’ in the traditional sense of the word because they struggle to do justice to what they have inside and yet, whatever they produce, it will never quite cut it compared to the personal sense of worth that they felt on the inside while crafting it.
The piece of art (or fiction) thus becomes a production where the reader or observer will have to go ‘the final mile’ himself in order to try and understand the full meaning of the piece and that’s one of the qualities that people tend to associate with good art; that it isn’t “complete” or “too dumbed down.” But in the case of the Fi types, their art doesn’t end up that way because they plan it like that – it’s because they naturally struggle to express themselves.
On the other hand, Fi types typically don’t care so much about rules and impartiality. They care about following their own heart, and if their own heart impedes them to do something wild, untraditional, or inappropriate, they don’t tend to stop and analyze whether that is fair or good in a judicial way, like the Ti types have a tendency to do.