Re: Terms: I.S., I.P., Neijin, Fajin, Aiki, etc.
The mixing, blending, combining? These words may well have been used in certain arts in the past and even today but they are not the terms mostly used by O'Sensei and thus his meaning for AI KI or even Ki.
He most usually used the words harmonizing, harmonizes.
Well, Ueshiba did sometimes use the term "harmonize", but much more often that's a mistranslation of the kanji for "Ai", which doesn't really mean "harmonize" in the sense that native English speakers usually use it.