I try to avoid the words "feeling" and "thinking" outside of their typological context. I don't really know the cognitive difference between thought and emotion — I mean, does anyone? Also, if the T/F dichotomy was really so strict, feelers would be incapable of logic and mathematics. Ability to think reasonably and even think at an impressive level obviously has nothing to do with being a T or F. My psychology teacher is an INFJ (don't know his enneagram, I'm betting it's 9w1) and he is extraordinarily intelligent.
Ti is inclined to make logical sense of everything whereas Fi is inclined to make judgments of value (e.g., what matters to me and why it matters). A person with strong Fi could actually decide to themselves, "Wow, math, science, and logic have made amazing breakthroughs for humanity. This is valuable." That person could then go on to become a theoretical physicist, a mathematician, an architect, a computer scientist, etc. Sensible and logical things can be valued, but emotional things really can't be analyzed, scrutinized, or made sense of. I think this could be why it's more usual for an INFP to be a 5w4 than an INTP to be a 4w5. Indeed, enneagrams for thinking types are actually 5, 6, and 3 for the intuitives and SPs and 1 for the SJs.
All too often Fi is associated with squishy moral values and gut feelings. That's total bullshit. INFPs aren't dysfunctional, capricious disasters and they aren't saccharine AT ALL (maybe some of the girls, but the guys tend to be very serious, poetic and/or artistic, philosophical, and very withdrawn). Poets and philosophers are often very erudite and although many would call those breeds 4w5 and 5w4 respectively, I think that's putting the cart before the horse. Why can't a poet be a 5w4? Is there no intellectual element in poetry or poets? Why can't a philosopher be a 4w5? You're telling me there's not a whole lot of individuality and self-expression in philosophy? You must be kidding! I should also note that 4s and 5s tend to have similar problems; I would also say both INPs suffer from similar problems.
So, why can't knowledge and learning be valued? If you ask me, wisdom and learning means a lot to most INFPs. I could easily see why it motivates them, especially since INFPs want to "have meaning" and "be known for their ideas." Both of these desires/motivations can be conflated with either enneagram; it really just depends on the INFP.
In truth, an Fi system of value might not be an ethical one at all! It might just involve what they find important. When you sketch Fi as the function that values things and Ti as the function that makes sense of things, it becomes clearer IMO. All this ethics vs. logic talk I hear is fucking stupid and makes no sense.
Anyway, I apologize for the novel. This is just a bundle of thoughts I've had stewing in my brain for a while.
