One of the best defenses I have for this theory is how I feel about martial arts in general – in the end, it is just a person with a stick. All martial arts must be based on the human body; how it is put together, how it moves, it's strengths and it's weaknesses. All weapon-based martial arts will be variations on how the human body uses a stick. This stick may be short, long, really long, pointed, sharp, straight, curved, etc. but it is still a stick. Any martial arts based on the human body (all of them) and on the same type of stick (a Medieval longsword) must, at their most basic level, be similar, if not identical.
As a follower of the Italian tradition, the techniques and principles of the German and English traditions are not alien to me. In fact, I have made it a point to study German longsword through books, seminars, and events, in addition to studying Italian longsword. I believe this kind of cross-training in similar arts to be extremely useful to more advanced students. (I say “more advanced” because it is necessary to have a solid base of experience with your chosen weapon or art before you begin to explore – otherwise you will be attempting to stand your art on a pillar of sand. Even the modern exemplar of mixing-and-matching in martial arts, Bruce Lee, recommended a solid grounding in one art before expanding.) However, I would never teach the 5 Meisterhau in a beginning Italian longsword class – they are simply not in the Italian system. Are they cool? Yep. Would I ever use one of the Meisterhau in free-play? You betcha, because they have been added to my “tool box”. Fiore tells us that he studied with German and Italian masters – so do I.
Studying other traditions gives you extra tools not only in technique but also for interpretation. Sometimes, looking at the way another tradition handles a certain situation can kick-start your own interpretation by acting as “Frog-DNA”. The challenge is to remain honest – if you borrow a technique from another system, make sure when you teach that technique to explain where it comes from. The same applies to any technique which you extrapolate.
But it is a very long step to say that these separate traditions are all the same Art. We know that medieval people traveled around, both in peace and in war, and that a cross-pollination of ideas occurred. But there is no denying that the longsword art of Fiore looks different than the longsword art of Liechtenauer; that Italian rapier looks different than Spanish; that Bolognese sword and buckler looks different than Silver's, and that both look different than I.33. This is because these arts were developed in different geographical regions, with their own cultural quirks and biases. One should expect Italian, German, English and French swordsmanship to differ just as the culinary arts from each of those areas differs. This cultural diversity is what makes what we do so freaking cool! If we all practiced the same art, life would be depressingly boring.
Is there “One True Art of the Sword”? Yes! But each tradition will be unique in how it approaches that ideal (I'm being very Platonic aren't I?).
So what is the “One True Art of the Sword”? To quote the 1998 movie “The Mask of Zorro”:
“The pointy end goes in the other guy”
For once Hollywood got it right!