Re: What makes Aikido aikido (to you)?
Mark is taking the genealogical approach with his item 1. He takes the functional approach with his item 2. And then the conceptual approach with his items 3) and 4). over all it is not bad as an approach . However, I think items 1 and 2 lack grounding in failing to explain what O Sensei changed, removed, added and why, and so the comparative dimensions definition is not really adequate.
As to item 2), the "internal skills" debate has not produced much in the way of generally agreed objective defining characteristics of what "it" is, how it may be concretely recognized or measured. Despite useful explorations along the way in near 1500-plus posts, spawning its own subforum, those debates (with some notable exceptions), have mainly boiled down to disputes over labelling or bona fides. Added to this is a general agreement (deeply mourned in some quarters) that O Sensei did not feel the need to teach "it" explicitly, whatever "it" may be deemed to be in objective terms. So that may not be the best basis for definition since everyone will likely read into it what they bring to it.
My definition is more addressed to the principal premises of the art as expressed by O Sensei. This leaves drawing concrete conclusions from them as a practical exercise for the teacher and student.
Straying very little from O Sensei's own words, I see them as follows
1) Love is THE true budo.
Love is the supremely effective basis for martial arts. As a low order statement it may be said to surpass both rage and calculation (the most readily identifiable alternatives) in its power and efficacy. As a high order statement, one could maintain that no other basis for martial action is effective (individually or collectively) without the presence of love in some regard, (even if most minimally as self-love).
2) Correct victory is self-victory. Masagatsu agatsu.
True love removes distinction between oneself and the other. Thus the first condition of true victory is to love the enemy as yourself.
3) Katsu hayabi. Victory is instantaneous.
Joining wholeheartedly with the expressed will of the enemy. The opponent cannot effectively oppose his own will -- without defeating himself. He attacks, I welcome him; he withdraws, I send him on his way. There is absolutely no resistance in aikido.
4) Takemusu Aiki. Conflict and creativity joining in spirit.
Love embraces all equally -- the form of the sphere. Energy is received and returned in a sphere. Attacking energy is in the form of line or point -- directed at the center point of the target; withdrawing energy flows directly back to the center point of the attack.
The characteristic dynamic shape of the art thus relies on tangents, centripetals, and rotations for gathering and releasing the energy of attack. The manner of articulating the body in gathering and releasing dynamic energy is also characteristic of offering, opening, and embracing. It is embodied in certain exercises intended to train it. Between the center point and the extreme limits of the sphere and anywhere along its surface, paths following the shape of the art and articulating the body in the characteristic manner provided for the art are infinite and free everywhere -- saving only the line of immediate attack.
5. Aikido also uses some Daito-ryu and weapons forms selected to organize its practical training and as illustrations of the operation of these definitional principles in controlled constraints.