For example watching something being tortured would bring up images or "feelings" similar to things the user has experienced and from there they would act in accordance to what they would deem to be right based on these essences which are under the control of the user. Basically it seems like Fi is the impetus to act or decide/reason on things. It seems like they build more validity and "truth" based on how deep the event that left an imprint or how much self reflection was done.
Like sometimes with Ti I will forgo rigorous analysis and rely on a more heuristic process, like a template, when coming to a conclusion. Sometimes when I'm not truly familiar with a topic it seems like I call on a number of different templates that I intuitively assume would mesh well together with the situation and I used those to come up with my conclusion.