Ne’s speak through ideas, Fe’s speak through emotions.
Ne’s tell you about their dreams and the psychology book they just read; they are excited to hear what you have to say and if any of your ideas align with or contradict what they just read; they speak with such enthusiasm about ideas, other people may think they have far more of an emotional investment in those ideas than they actually do. It’s a bit like a puppy with a bone. It’s great, he loves it … and then he sees a bigger bone, and drops the first without a second thought. The first bone may or may not catch his attention ever again. Ne’s can seem out of touch with reality due to their idealism – their Ne teaches them to see an ‘ideal,’ the absolute greatest potential something can reach (a perfect person, a perfect day, a perfect concept) and they want to believe it’s possible. So they give idealistic advice. They push people to try their hardest. And their standards may seem unattainable as a result. But as a friend of mine said, “We’re all in the gutter… but some of us stare at the stars.” Watch them. Their IDEAS change.
Fe’s tell you about their emotional interactions, their desire for unity, their reactions to things, how they feel about the ethics of this or that, the behaviors they will and will not tolerate, what they believe, and can be incredulous when others do not have the same standard of ‘emotional openness’ that they do. They try to merge with you, to include you, to be in harmony with you. If they change, their emotions change – not necessarily their ideas – and it’s often because they saw something from your perspective and it seems wrong to them not to see you as an equal and treat you with respect, even if they disagree. Depending on the level of health / development, this can manifest in Fe ‘pushing’ a moral concept on you or trying mightily to change your mind (since that you do not agree bothers them); or in being weak, and more desirous of harmony or inclusion, so their values shift based on the stronger voices in the group.
In short:
Ne: changes their mind because a better idea came along
Fe: changes their mind due to a persuasive argument or external pressure