When describing the term / concept “Indes” it is sometimes defined as meaning “simultaneously.” But I belive we must be careful that Indes does not literally mean acting “simultaneous.” Rather, it means more “in the same instant” or “just as”. I am convinced trying to apply the concept as meaning “simultaneous” leads to misunderstanding (and edges bashing on edges). This is easily enough to demonstrate in person with weapon in hand, but for example, consider that one can strike either before, during, or after the opponent makes his own action. The before and after are easy enough to understand as taking advantage of the opening created in the opponent’s timing. But the “during” is more subtle. If two people strike independently at the very same time, so that their actions coincide, this would definitely be “simultaneous” (and such does happened on occasion in fighting).
Yet the idea in striking with Indes is to first perceive the opponent’s own intent to strike and then, just as they make their strike, to react in the same instant during their motion so that your own counter-strike succeeds instead. Thus, the fighter does not really move “simultaneously” because he must first detect the opponent’s action, make the decision to act himself, and then make his own action –all in the briefest instant. The Indes is dynamically responsive. His action is not independent, but dependent on his intent at countering the adversary’s in the middle of their motion. The two actions do not just coincide in time, rather there is a relationship of cause and affect. Strike before he really commits to his attack and you are moving in Vor, wait longer and you act in Nach/Noch. Paradoxically, when you try to counter-strike with Indes, if you attack too soon you can be hit after by his own Nach, while if you start your attack too late he can hit you in Vor first. Indes is I believe the same as the "Volarica" principle of Vadi.
Make sense?


