Martial Arts are simply (at a minimum) a system of techniques that when employed a practitioner can use to defeat an opponent. That's it. Any augmented requirements such as Budo, for instance, simply came about because they conditioned practitioners mentally in a way that made them more combat effective. Anything that is superfluous in that it cannot implicitly or explicitly be reasoned why its inclusion helps the martial art achieve this goal has nothing to do with the art itself. And of course, such reasoning is relative to the individual.
How effective a martial art is, or how well it solves the dilemma proposed to all martial arts, greatly depends on the context in which it is employed. "Armed" combat, be it any of the (probably) thousands of style of swordsmanship, hybrid styles, empty hand styles, marksmanship, disarmament styles etc. are all "martial arts". Just as important is the practitioner himself. He is inseparable from the art.
Of course, one must define "defeat" in the context of combat. Aikido proposes that to "defeat" an opponent, one must simply preserve oneself from injury in any number of scenarios. Boxing proposes the opponent will suffer defeat by winning a contrived bout by a judges' decision or knockout within a certain ruleset and so fourth. We are told there are "No rules, basically", in an "open arena". Can weapons be brought in by our celebrities? What about friends? You might call these questions trivial and sophomoric in the sense that the answers should be "obvious", but it doesn't mean that one can assume the answers to them to be a certain way.
And the competitors themselves must be able to have sufficient responses to the answers of these questions. It is one of the reasons why early MMA was so inconsistent and chaotic: most of the martial artists that competed never even considered that their system might be presented with questions that were outside of the design of the system, let alone have answers for those questions. Even though modern MMA has become so mainstream that there are now a bunch of templates in which most athletes fall, some still find room within the ruleset to put together questions none have a notion of how to answer it when the time comes. Jon Jones is a 6'4" light heavyweight with an 84" reach and genetically gifted in a way (his brother, Arthur, played football at Syracuse and was selected 5th round by the Ravens as a DT, and his other brother, Chandler, is a DE @ Syracuse) not seen before in professional MMA promotions. Unorthodox striking techniques and unmatched greco-roman skills give him the ability to purpose such questions, despite the idea that all such questions within the context of the Unified MMA ruleset have been asked and answered. BTW, his next fight is free on Sunday, on VS...
No system can answer all possible questions, because that would, by definition, make it to be unbeatable. Even if the system of techniques could theoretically be used to obtain victory in any circumstance, the case cannot be made once the human is considered. This is more evidence that the practitioner and his art are inseparable. Of course this notion makes sense when rationalized: a system of techniques that cannot be physically implemented is useless. But not all practitioners are equal. This is where I reject many of the notions purported by the Gracie family, because they are too absolute in nature. Or, to put it another way, in response to the well known Gracie saying that "90% of fights go to the ground, whether by accident or design", Shawn Tompkins once said "That may be true, but it is my understanding that nearly 100% of fights begin standing."
Anyway, as that applies to this discussion, I find these kinds of arguments to be rather fantastical. Which isn't to say there's no use for such arguments. This is the Entertainment section, after all.