p. 366: "Introverted Feeling ... encourages a personal relationship to an evolving pattern, a will to gauge the situation by an experiential ideal. For example, if we use Introverted Feeling to make a good spaghetti sauce, we won't follow recipes or measure ingredients. We'll sample the sauce as we're making it, gauging its taste, smell, and texture by their ideal outcome and adjusting for circumstantial variables so the emerging pattern stays on track."
p. 367: "To invoke Introverted Feeling, we have to know the difference between a good outcome and a bad one--know with our senses, in our bones [on the basis of living, breathing, first-hand experience]."
p. 371: "An inner point of reference, one trained by personal experience. [Bypassing matters of social standing] to focus on the quintessentially human."
From this attitude, each living thing is completely unique, and has unique needs. Every living thing needs to express itself and grow in its unique way. None of this can be put into categories or measurements, at least not without blotting out that utter uniqueness of each living thing.
Fi leads IFPs to live a life based on empathy and harmony between self and others--and/or to see life as a never-ending conflict between souls that are intrinsically different and opposed. ISFPs typically seek out a space in which they can be completely and spontaneously themselves, following their artistic impulses without regard to social expectation or definition of any sort.