+Fi: that which draws you to others (that which you want)
-Fi: that which draws others to you (that which others want from you)
I say this only with regard to the aspects themselves. not the elements.
Although + and - are often described as "that which one has" vs "that which one lacks", I see this as a problematic appraisal. Particularly, they both seem to be concerned with the production of new content, which they guage as lacking relative to their content level of their contraries of the opposite sign. (-Fe and +Fe in the case of ISFjs/INFjs) Thus there is always a lacking -- that's part and parcel of the problem.
I say this with regard only to the elements themselves, not their functions. On the other hand, there do appear to be problems with this view.
I'm not satisfied that this position is the correct one. Please critique.