费曼在1965年因为量子电动力学方面的贡献与施温格、朝永振一郎分享了诺贝尔物理学奖之后，收到了来自世界各地的大量来信。他之前的一个博士生，Koichi Mano，也发信来祝贺。Koichi Mano曾经也是朝永振一郎的学生，于1955年获得博士学位，是费曼在加州理工学院（1951-1988）最早的一批博士生之一。
费曼回信问了Koichi Mano现在在做什么，得到如下答复：“研究相干理论及其在电磁波通过湍流大气传播中的一些应用…一个卑微的、偏实际类型的问题（a humble and down-to-earth type of problem）。”
可惜你的信也让我有些不快，因为你看上去很伤感。似乎你老师的影响，让你对什么是有价值的问题产生了错误的观念。有价值的问题是那些你能够真正解决、或者有助于解决的问题，是那些你能够真正做出贡献的问题。如果有一个问题摆在我们面前尚未解决，而我们能找到一些方法往前推进一点，那么它就是科学方面的重大问题（grand in science）。我倒是想建议你，在找到可以真正轻松解决的大问题前，先找一些更简单的，或者如你所说的，更卑微（humbler）的问题来做，不管多么无足轻重（trivial）。这样你会尝到成功的喜悦，并从帮助你的同事中获得快乐，哪怕只是回答了一个能力不如你的同事所思考的问题。千万不要因为大问题才有价值的错误观念剥夺了自己的这些快乐。
你在我职业生涯的巅峰时期遇见了我，当时在你看来，似乎我关心的问题都是很高大上的（close to the gods）。但同一时期，我还有另一个博士生Albert Hibbs在研究风是如何吹在海洋中的水面上形成波浪的。我接收了他当学生是因为他带着想要解决的问题来找我。我对你犯了一个错误，我直接给你指定了题目，而不是让你去找到自己想要解决的问题，并让你对什么是有趣的、令人愉快的、或是重要的工作（也就是那些你认为你或许能做点贡献的工作），留下了错误的印象。抱歉，请你原谅。我希望这封信能补救一点点。
原文如下（收录在《Perfectly Reasonable Deviations from the Beaten Track —— The letters of Richard P. Feynman》一书中）：
A former student, who was also once a student of Tomonaga’s, wrote to extend his congratulations. Feynman responded, asking Mr. Mano what he was now doing. The response: “studying the Coherence theory with some applications to the propagation of electromagnetic waves through turbulent atmosphere… a humble and down-to-earth type of problem.”
I was very happy to hear from you, and that you have such a position in the Research Laboratories.
Unfortunately your letter made me unhappy for you seem to be truly sad. It seems that the influence of your teacher has been to give you a false idea of what are worthwhile problems. The worthwhile problems are the ones you can really solve or help solve, the ones you can really contribute something to. A problem is grand in science if it lies before us unsolved and we see some way for us to make some headway into it. I would advise you to take even simpler, or as you say, humbler, problems until you find some you can really solve easily, no matter how trivial. You will get the pleasure of success, and of helping your fellow man, even if it is only to answer a question in the mind of a colleague less able than you. You must not take away from yourself these pleasures because you have some erroneous idea of what is worthwhile.
You met me at the peak of my career when I seemed to you to be concerned with problems close to the gods. But at the same time I had another Ph.D. Student (Albert Hibbs) was on how it is that the winds build up waves blowing over water in the sea. I accepted him as a student because he came to me with the problem he wanted to solve. With you I made a mistake, I gave you the problem instead of letting you find your own; and left you with a wrong idea of what is interesting or pleasant or important to work on (namely those problems you see you may do something about). I am sorry, excuse me. I hope by this letter to correct it a little.
I have worked on innumerable problems that you would call humble, but which I enjoyed and felt very good about because I sometimes could partially succeed. For example, experiments on the coefficient of friction on highly polished surfaces, to try to learn something about how friction worked (failure). Or, how elastic properties of crystals depends on the forces between the atoms in them, or how to make electroplated metal stick to plastic objects (like radio knobs). Or, how neutrons diffuse out of Uranium. Or, the reflection of electromagnetic waves from films coating glass. The development of shock waves in explosions. The design of a neutron counter. Why some elements capture electrons from the L-orbits, but not the K-orbits. General theory of how to fold paper to make a certain type of child’s toy (called flexagons). The energy levels in the light nuclei. The theory of turbulence (I have spent several years on it without success). Plus all the “grander” problems of quantum theory.
No problem is too small or too trivial if we can really do something about it.
You say you are a nameless man. You are not to your wife and to your child. You will not long remain so to your immediate colleagues if you can answer their simple questions when they come into your office. You are not nameless to me. Do not remain nameless to yourself – it is too sad a way to be. Know your place in the world and evaluate yourself fairly, not in terms of your naïve ideals of your own youth, nor in terms of what you erroneously imagine your teacher’s ideals are.
Best of luck and happiness.
Richard P. Feynman.