Lipyeow... "Aiki" is the Unifying the Mental with the Physical inside yourself. Then, it becomes Unifying Yourself with the Opponent.
Ueshiba's Aiki was that. However, his son Kisshomaru eliminated the internal elements from the modernized approach to aikido that became the Aikikai method... which was the mainstream, mass-introduced aikido sent out around the world by the young missionary teachers who were rapidly trained and promoted in that new version.
Without the internal methology that provided stable, unified power and connectivity, and peng, the new aikido had to devise a new strategy to make the existing waza work. Instead of being able to stick into, draw in and "smother" to control the opponent (old Daito-ryu strategy), aikido training became mainly about using a combination of externally driven evasive movements and mental manipulation of the opponent to lead him into overreaching his limits (his center or one-point) when attacking (no 13 points to hold his alignment and structure), so that he loses his own center and is thus easier to control and manipulate.
Joint locks and pins are also used, but without aiki to power it (which would control the opponent's entire frame, structure and center. Locks and pins using aiki make it possible to freeze the opponent's frame and movement without needing to use pain.), the user must rely on timing, leverage and pain compliance.
This is NOT necessarily a bad thing. In my observation, aikido, at its higher levels, can work very well against an unsuspecting opponent who is not "internally" trained. With the right training, someone absolutely can become a master at leading the mind of an attacker, and thus his body, and hone timing to an exquisite level. Even though the powering methods are external, mastering the mental aspects goes a long way to making aikido waza work, IMO. Also, there are some vestiges of Teh Internalz that manifest themselves in "jin tricks" (e.g. the arm as a hose full of water... etc.) and some of the kokyu training that can lend some aspect of power and structure to aikido. But having the full monty of aiki and IP would add so much more...
The problem is that a little bit of knowledge is a dangerous thing, so students can put too much faith in intermediate-level experience. What works in careful training in the dojo might not be street-ready yet. And that's one reason not to be overly compliant in the dojo. Failure is an important learning tool. The sensitivity it takes to be able to lead minds into a hole, takes years to master. Especially minds of attackers who are not aikidoka, or who are psychotic, and want to take your head off.
Okay, that's it for me, for injecting additional controversy to this Controversial Thread, which Lipyeow, started by whacking the hornets' nest with a stout stick.