菲利普·弗兰克Philipp Frank

菲利普·弗兰克的父亲是Ignaz弗兰克，母亲是Jenny Feilendorf。弗兰克在维也纳大学学习物理学，在路德维希·玻尔兹曼指导下工作后，于1907年获得理论物理学博士学位。他这样描述他的学生时代（例如见[1]）：-

……我最投入兴趣的领域是科学哲学。我过去常与一群学生交往，他们每周四晚上都会聚集在维也纳的一家老式咖啡馆里……我们一次又一次地回到这个核心问题：我们如何避免哲学传统的模糊性和晦涩？我们如何才能使哲学与科学尽可能紧密地接近？

弗兰克在这段引文中描述的学生群体，就是最终被称为维也纳学派的那群人。当时这个群体的其他成员还有汉斯·哈恩、von 理查德·冯·米泽斯，以及一位经济学家兼社会学家Otto Neurath。这个群体发展了逻辑实证主义哲学，研究科学语言和科学方法论。在此期间，弗兰克成了von 理查德·冯·米泽斯的朋友，后者于1907年在维也纳获得博士学位，与弗兰克同年。这是一段持续终生的友谊，并涉及合作研究。

1907年，弗兰克写了一篇关于因果性的重要论文。阿尔伯特·爱因斯坦对弗兰克在这篇论文中提出的思想印象深刻，由此产生的讨论促成了另一段终生友谊，这次是在弗兰克和阿尔伯特·爱因斯坦之间。两人都热爱科学哲学，彼此的思想相互影响。弗兰克获得了他的教授资格论文（Habilitation），并于1910年被任命为维也纳大学讲师。在阿尔伯特·爱因斯坦的推荐下，弗兰克于1912年接替他担任布拉格德国大学理论物理学讲席。

弗兰克、汉斯·哈恩和理查德·冯·米泽斯成为20世纪20年代活跃于维也纳逻辑实证主义学派中一个稍大群体的一部分。对他们思想的重要影响来自其他几位对哲学感兴趣的数学家和科学家：波恩哈德·黎曼、赫尔曼·冯·亥姆霍兹、海因里希·鲁道夫·赫兹、路德维希·玻尔兹曼、儒勒·昂利·庞加莱、大卫·希尔伯特和阿尔伯特·爱因斯坦。在哲学方面，影响则来自戈特洛布·弗雷格、伯特兰·罗素和阿尔弗雷德·诺思·怀特海。弗兰克在描述他如何感到科学、数学和哲学相互联系时解释说[1]：-

……他始终寻求对人与自然获得一种平衡的看法；对他而言，物理学不仅为具体技术问题提供了可靠的答案，还提出并阐明了关于人类知识的性质、范围和有效性的重要问题。……[他]相信，通过现代自然科学的批判性、理智的方法，最能实现对生活的稳定看法。

弗兰克与理查德·冯·米泽斯之间的友谊在20世纪20年代中期发展成了合作。他们是1925年出版的两卷本长篇著作Differentiagleichungen und Integralgleichungen der Mechanik und Physik Ⓣ（《力学与物理学的微分方程和积分方程》）的共同作者。弗兰克于1920年11月16日结婚，妻子是Hania Gerson。

弗兰克一直留在布拉格德国大学直到1938年。那年的慕尼黑协定使捷克斯洛伐克共和国的大部分领土被割让给德国。德国军队连同希特勒本人已于1938年3月12日进入奥地利，并在那里建立了纳粹政府。政治压力被施加于弗兰克和维也纳学派的其他成员，该群体解散，包括弗兰克在内的许多成员逃往美国。

在美国，弗兰克先被任命为访问讲师，然后成为哈佛大学物理学和数学讲师。他的朋友von 理查德·冯·米泽斯也来到哈佛与他共事。1947年，弗兰克写了一部优秀的传记Einstein: His Life and Times。

弗兰克在数学的广泛领域中工作，考虑到他在物理学和哲学方面的出版物，其广度确实非凡。在数学方面，他研究了变分法、Fourier series、函数空间、哈密顿几何光学、埃尔温·薛定谔波动力学和相对论。

Philipp Frank's father was Ignaz Frank and his mother was Jenny Feilendorf. Philipp studied physics at the University of Vienna obtaining a doctorate in theoretical physics in 1907 after working under Boltzmann. He described his student days as follows (see for example [1]):-

... the domain of my most intensive interest was the philosophy of science. I used to associate with a group of students who assembled every Thursday night in one of the old Viennese coffee houses ... We returned again and again to the central problem: How can we avoid the traditional ambiguity and obscurity of philosophy? How can we bring about the closest possible rapprochement between philosophy and science?

The group of students that Frank is describing in this quotation is the group who would eventually become known as the Vienna Circle. Other members of the group at this time were Hahn, von Mises, and an economist and sociologist, Otto Neurath. The group developed the philosophy of logical positivism, investigating scientific language and scientific methodology. During this time Frank became a friend of von Mises, who obtained his doctorate from Vienna in the 1907, the same year as Frank. It was a friendship which would last throughout their lives and involve joint work.

In 1907 Frank wrote an important paper on causality. Einstein was impressed by Frank's ideas which he put forward in this paper and the resulting discussions led to another life long friendship, this time between Frank and Einstein. Both loved the philosophy of science and the ideas of each would influence the other. Frank received his habilitation and was appointed a lecturer in the University of Vienna in 1910. On Einstein's recommendation Frank succeeded him to the chair of theoretical physics in the German University of Prague in 1912.

Frank, Hahn and von Mises became part of the somewhat larger group active during the 1920s in the Vienna Circle of Logical Positivists. Important influences on their thinking came from several other mathematicians and scientists interested in philosophy: Riemann, Helmholtz, Hertz, Boltzmann, Poincaré, Hilbert, and Einstein. More on the philosophy side, influences came from Frege, Russell and Whitehead. Frank, describing how he felt that science, mathematics and philosophy were linked, explained that [1]:-

... he sought always to achieve a balanced outlook on man and nature; and for him physics not only provided reliable answers to particular technical problems but also raised and illuminated important questions concerning the nature, scope, and validity of human knowledge. ... [he] believed that a stable perspective on life can best be achieved through the critical, intellectual method of modern natural science.

The friendship between Frank and von Mises developed into a collaboration in the mid 1920s. They were joint authors of the lengthy two volume book Differentiagleichungen und Integralgleichungen der Mechanik und Physik Ⓣ which was published in 1925. Frank had married on 16 November 1920, his wife being Hania Gerson.

Frank remained at the German University in Prague until 1938. The Munich Agreement in that year saw large parts of the Czechoslovak republic surrendered to Germany. German troops along with Hitler himself had entered Austria on 12 March 1938, and a Nazi government had been set up there. Political pressure was put on Frank and other members of the Vienna Circle, and the group disbanded with many of its members including Frank fleeing to the United States.

In the United States Frank was first appointed as a visiting lecturer, then made a lecturer in physics and mathematics at Harvard. He was joined at Harvard by his friend von Mises. In 1947 Frank wrote an excellent biography Einstein: His Life and Times.

Frank worked on a wide range of topics in mathematics, and when one takes into account his publications on physics and philosophy it was a truly remarkable breadth. In mathematics he worked on the calculus of variations, Fourier series, function spaces, Hamiltonian geometrical optics, Schrödinger wave mechanics, and relativity.