Sen is a Japanese term that means before, or ahead. Sei means life, birth or living. Therefore, the sensei is a teacher. They are born before, therefore they are thought to have knowledge that inexperienced people do not. Therefore I broadly understand a sensei to be "one who has gone before".
In the karate environment, a sensei is seen to be a "teacher" or an "instructor", and therefore the term implies many year’s experience, and the achievement of high order of karate skills and knowledge. Further it implies the ability to teach others of a lower grade, and contribute to their development.
In the dojo environment "sensei" also implies "leadership", and so the criteria for a karate sensei will be very similar to the criteria required for anybody in a leadership position. Throughout history there have been numerous attempts to clearly identify "what is leadership".
In trying to define the criteria of a sensei, one necessarily must assume a moral position first, and therefore the criteria really refers to an "outstanding", or "ideal’ sensei. One could equally make a list addressing the negatives, or simply be neutral. As the following list implies "superior" human performance by it’s very definition, it is not possible to empirically identify whether any particular individual sensei has "passed" the supposed "test". The list is also deficient in it’s omissions rather than it’s inclusions.
In any event, who is the judge? What human being would advance a definitive and conclusive answer to this question? The answer to the question lies in two places: our own hearts, and in God’s grace.
Nevertheless, imperfect as it is, and with humility scorched by the fire of egotism, here is my first, tentative, preliminary, draft list:
A sensei has a good understanding of teaching principles. A sensei has the ability to plan and deliver meaningful instruction, taking into account the varying needs, interests and abilities of others.
A sensei is an "extra-ordinary" person, and is seen by others to be "different" and "more advanced" in crucial areas of human life.
A sensei is a human being who tries at all times to "do their best" for others. They are concerned about other’s needs and concerns. They are good counsellors and help people work through problems.
A sensei understands and applies modern bio-mechanical and human performance principles to ensure a safe training environment.
A sensei is up to date, and maintains qualifications and expertise in first aid, teaching skills and effective management practices.
An effective sensei should have impeccable human relations skills, and has the ability to "lead" others. He is able to develop and maintain harmonious and effective relationships. A sensei who is surrounded by turmoil and "staff turnover" of senior students is not an effective sensei.
An effective sensei is fair and impartial, with no "favourites". In dealing with others and making decisions, the sensei is seen to be fair to everybody. Fairness is defined by other people, not the sensei, so the sensei is alert to the feelings of other people.
A sensei instills, and develops others confidence in themselves.
The ability to effectively employ verbal, written and listening skills is crucial to be a sensei. The ability to communicate effectively is critical. Most leadership problems are caused through leaders being ineffective and one-way communicators.
A sensei has the ability to generate a "team" environment through effective maintenance of leadership skills. Recognising and rewarding effort, and treating other people with fairness and dignity is crucial.
A sensei always looks for and finds the best in other people, concentrating on the positives.
A sensei has the skill to solve problems intelligently and with human relations skill, so that effective outcomes are achieved in an harmonious and realistic fashion.
An effective sensei is intelligent and therefore able to act wisely. The sensei has the ability to "think through" issues and see with "spatial vision" to identify the potential outcomes from a course of action.
A sensei is honest and transparent. There is no "dualism".
A sensei is ethical in all his dealings.
A sensei is not a true sensei if others are unwilling or unable to follow the sensei.
A sensei is "human", and understands and forgives himself and others. A sensei can admit an error, and say "I was wrong".
A sensei has a highly developed "self insight" and is able to "see themselves" as others see them, act accordingly, and are therefore able to be at peace.
A sensei uses discretion and honours confidences.
A sensei understands and uses "honourable" behaviour.
A sensei is a role model for moral, ethical and legal conduct.
A sensei is not a vindictive or angry person. They do not "punish". They understand students come to the dojo of their own free will, and are not "conscripted".
An effective sensei lives in the "real world", and is not isolated from other people and their issues. He is flexible and understands that everybody who persists at karate tries their best, even if it’s not what the sensei wants.
A sensei does not think or act as if he’s better than anyone else, either as a karateka, or as a human being.
A sensei is polite, calm and courteous to all people at all times, no matter what the provocation.
A sensei maintains a "beginners mind".
A sensei is grateful for all things.
A sensei is above all a human being who makes mistakes, and sometimes falters. With the support of colleagues and seniors they are however, able to overcome difficulties and grow.
If a sensei dies, retires, or is otherwise unable to continue teaching, that is the measure of a sensei. Will the students be devastated? Will they be unhappy because a great martial artist has gone, or because a great human being has gone?
It is impossible to adequately write down the criteria for a sensei, because it’s a feeling one has, and includes the ability to enter the fourth dimension of existence.
To be able to stand above a mountain top and perceive all directions is a rare gift. Not all sensei will reach this, but all would aspire to it. How does one describe the ability to see this way? It is not possible to write it down. The feeling and the understanding is from heart to heart. No human communication is necessary or possible. Human communication being inadequate to this task, the communication is silent, like one hand clapping.
Silent communication is the only way to adequately define the "Criteria for a Sensei".
Being imperfect, or not having yet reached the highest levels of human understanding and performance does not disqualify one from being a teacher or a sensei. It simply means the sensei still has to complete their own personal journey.
We will all be judged by our humanity, not our martial arts skills. This applies more so to a sensei.
What are the criteria for a sensei? The same as for a human being. Therefore one cannot be "inadequate" or not "fit".
One just "is".