There are few professions that impact future generations more than being a teacher. Not only do teachers teach students about history and science, but they teach students about the world. Through this teaching, students not only discover who they are, but who they want to become.

Days after Albert Camus became the second youngest person to win the Nobel Prize, Camus showed gratitude to whom it was due–his former teacher. Camus writes to Monsieur Germain:

Without you, without the affectionate hand you extended to the small poor child that I was, without your teaching and example, none of all this would have happened. I don’t make too much of this sort of honor. But at least it gives me the opportunity to tell you what you have been and still are for me, and to assure you that your efforts, your work, and the generous heart you put into it still live in one of your little schoolboys who, despite the years, has never stopped being your grateful pupil. I embrace you with all my heart.

With that generous heart guiding us, we shall appreciate all methods of teaching and learning.

But I'd be a fool to say all teachers are the same. Some care only about their students passing the tests. Some don't care at all one way or the other. Many are great experts in their fields, but don't have the unique ability to communicate that expertise to a mere novice.

So what is it that makes a great teacher? This is what Vannevar Bush explores in the penultimate chapter to his memoir Pieces of the Action (notes). Vannevar Bush was an engineer, inventor, and administrator who headed the U.S. Office of Scientific Research and Development (OSRD) during WWII. Bush reported directly to President Roosevelt. His book is a culmination of those experiences distilled down to the lessons Bush learned about dealing with "tyros", going toe to toe with Churchill, his philosophy on organizational structure, what's wrong with the patent system, how engines work, and for the sake of this article, an ode to great teaching.

Bush begins by laying out the foundations for a great teacher:

We can discern a few conditions that any teacher worthy of the name must meet. Clearly, he must know the subject he is teaching. But this does not necessarily mean that he must be a master of all its higher complexities. In fact, he may be all the better a teacher if he does not know too much, especially when he is dealing with introductory courses. If he is far enough ahead of his students to treat the subject with assurance, to be unafraid of their questions, and to be able to explore with them, that is enough. But there is a corollary: he needs to stay that way. Subjects alter and advance. So he has to be a student himself, avid to learn, willing to struggle to keep well ahead.

But this attitude doesn't mean the teacher has to know every answer. In fact, Bush commends the teacher that explores questions with this students as they themselves are learning about it. Quoting Oppenheimer, he writes:

"To teach a mistake is unfortunate; to teach indifference is a crime." Teaching indifference occurs, of course, only if the teacher himself is indifferent, if he is not really and genuinely interested in the subject. It is all right to say "I don't know" to a student or to a class, provided it is said in an answer to a good questions and carries with it the connotation "But let's find out."...I think it creates a fine spirit among a class when the professor says, "Well, now, that's a good question, but I can't give you an offhand answer. Let's see what we can work out," and starts to examine the thing in detail right before the class. This attitude is, of course, at the heart of nearly all good teaching in graduate school.

This spirit of honesty and openness is important for a classroom, Bush notes, because:

Much of the way in which classes regard their teacher depends upon whether they think the man is honest or just a poser doing some kind of act.

These practical matters are quite important in determining a teacher's value, but they're not everything. Like any great art, there are practical skills that are required for a bare minimum job, but also required are less tangible skills. For those, Bush writes:

This is the spirit of success, and the ability, the deep, subtle ability, to transmit it, the mysterious characteristic which inspires emulation. And be it emphasized again, this by no means implies just material success, although that should be included too. My most inspiring teachers led me to seek understanding that was not worth a nickel in this world's goods. It is intangible–this spirit–somewhat an aura, which the ablest teachers bring with them to lecture hall or laboratory or classroom or conference, and to which in definable ways the student mind and spirit respond.

The task of teaching in colleges is not merely to provide students with the skills necessary for a professional career and to prepare them for the bases on which informal collaboration with their fellows is facilitated, but to go beyond these and provide the foundations for associative relationships that may become worthy, not merely trivial, and which confer genuine satisfaction upon those who participate.

The importance of being a great teacher are of utmost importance for not only the present generation, but for future ones as well. Influencing the future to come is the main driving force behind Bush's philosophy for great teaching. He writes:

The basic function of education is to ensure that the experience of one generation may be passed on to the next. It is the ability to make this transfer that distinguishes man from beast.

Bush concludes the chapter with a declaration for different types of courses, allowing students to combine key ideas in one field and relate them to key ideas in another:

Thus, we need a balance. Alongside the course in the mathematics of electric circuits, we need a course in the history of ideas. And we need that balance wherever older minds seek to help younger minds on the way of life.

His last words on the subject of teaching come as an encouragement for teachers to remember the duality between what they're teaching–the actual course content–and how to be someone in this strange world:

What is true in the college classroom is true in the kindergarten as well. Every teacher, no matter his subject, needs to remember that he is preparing most of his students for a life marked by a great duality, one part as a tiny element in a complex social structure, the other in informal relations with their fellows. As he remembers this, and puts it to work in all he does, as he leads his student to be useful, but also to find joy in life, he is a great teacher.