What Use Lineage?
A traceable lineage neither guarantees a quality training environment nor a legitimate experience. One should also keep in mind that Asian martial arts have a tendency to embellish their relationships and lineages. For example, it's common in Japanese arts for a soke to claim he was the only student of his teacher, or for a practitioner to claim he studied under X, when in fact he studied under X's student Y.
Teachers Versus Lineage
There is a distinction between one's teacher and a full lineage. For instance, in judo, it's common to say "I study under Joe Blow", or "I train at Acme Dojo", whereas it's very rare to hear a judoka lay out the full lineage-chain back to Jigoro Kano. The same situation holds true in many Western arts such as boxing, and schools that focus on practical application. The perspective here is that the quality of one's teacher matters a great deal, but can be judged in itself, without needing to reach back further in history.
The opposite is true in many schools of karate, all Japanese koryu, and schools that focus on history and tradition. Being able to trace an authorized teacher-student relationship to the founder of the style is considered in those circles as the sine qua non of legitimacy.
Another form of legitimacy similar to lineage is membership in an association. In some martial arts, affiliation with a greater body is extremely helpful in establishing a basic level of credibility. In judo, you can ask (and double-check) if a school is affiliated with USJF, USJA, or USA Judo. In Brazilian jiu-jitsu, you can ask (and double-check) who they got their rank from, and in some situations, whether they are part of an association like Alliance, a Gracie branch, Atos, et cetera.
Note the differences between affiliation and lineage: it is current instead of based in history, it sometimes involves insurance coverage (such as in judo and many forms of Korean karate), and while informative, it is generally not considered a test of legitimacy in itself.
If one does not subscribe to the idea that legitimacy is transmitted solely through lineage, one must take on the task of evaluating the legitimacy of a school. This is a very broad task and should take into account many factors, such as:
- The practical ability of a teacher, best assessed through a competition record or direct experience (e.g. sparring)
- The pedagogical ability of a teacher, best assessed by observing their students' behavior in life, competition, and class
- The environment of a school, best assessed by going there and training
If one of your goals for training martial arts is to learn to fight, then the first one of that list is important. As Matt Thornton notes:
If you want to know if someone is "good" at fighting, or teaching some element of fighting then you must:
A) Watch them spar, or pull off their movement against a resisting opponent. or
B) Watch the "Instructors" students spar, or pull off their movement against a resisting opponent.
There is really no other way.... Anyone can 'look good', even 'look crisp' hitting focus mitts. Or demonstrating one and two step sparring, etc. It has ABSOLUTELY nothing to do with whether or not they can actually fight, or know how to teach anyone else how to fight. All it means is. . .they know what they think it should 'look like'.