By the beginning of the 20th century, there were many people who try to axiomatize thermodynamics. 我认为it’s not a very useful thing. Physics is about reality, and reality is very complicated. It’s not like Euclidian geometry you can axiomatize. If you want really to be absolutely logical, you have to state many many things before you can be completely sure. So the idea axiomatizing physics, in my opinion, is a useless thing. The reason there were discussions of axiomatizing thermodynamics was because, at the end of the 19th century and the beginning of the 20th century in mathematics, through, especially, the leadership of the great mathematician Hilbert, there was an idea to axiomatize mathematics in his 23 problems. Hilbert in the year 1900 gave a famous speech about 23 important problems in mathematics, and that caused the tremendous influence on 20th century mathematics. One of these 23 was to axiomatize physics, in my opinion, that is not the right direction. Around 1930 there was a young mathematician named Gödel who showed that the whole idea of axiomatizing the whole mathematics is not quite right thing to do, that's a great development in mathematics, in mathematical logic and in philosophy. Then without having achieved the axiomatization of physics, they lost of interest about this Hilbert problem until the 1950s. In the 1950s elementary particle physics entered into a period of searching for the future, some people, especially many people in Germany, in some senses were reviving this idea of axiomatizing physics, and that was picked up by a number of people over the world. So it became a field called the axiomatic field theory, but by the 1970s that died again. It's today such kind of effort in such a direction is not considered to be a useful way to push physics forward. So we are trying to be physicists and not logicians in discussing physics. 后记:2004年秋季学期,杨振宁在清华大学给大学一年级学生讲授普通物理。清华大学对杨先生的全部讲授都录有视频,并留存了全部讲稿,但是,这些资料一直没有公开。疫情初发的时候,视频网站上出现了杨先生讲课的视频共30讲。第23讲讲到卡诺定理的时候,他提到卡诺循环是一个理想的可逆循环,而这一理想的情况却不是真实存在的。也许是受这个问题的触发,在课堂上(视频35:55-39:50),杨先生就公理化热力学和公理化物理学的历史进行了简要的回顾,并表达了自己对物理学的公理化的看法。公开发表的文字材料中,杨先生从来就没有如此明确地反对物理学的公理化。而这一段话非常具有启发性,值得摘录出来公之于众。原文是的较为随性的议论,笔者整理成为较为正式的演讲,然后翻译成为中文,中文中的重点标记为刘全慧所添加。 摘录这段话还有原因。2023年4月份,“纳米热力学读书会”中的专家学者中讨论了物理学公理化的问题,很多名家发表了看法,至今还有讨论。笔者认为,从归谬法看物理学的公理化,可以立即得到一个明确的结论。如果物理学能公理化,就成了数学的一个分支。而数学的正确性是靠逻辑来保证的,完全不需要实验。不需要实验就不是物理学了。当然,这仅仅是一个粗线条的想法,不足以解决所有的问题。 最后是一个广告。2023年7月9日至7月24日将在兰州大学线下举办“纳米随机热力学暑期学校”,课程内容将在蔻享学术平台同步直播,并留有回放。授课专题包括:1.热力学与统计力学基础;2.概率论基础与高级概念;3.约束优化与对偶性;4.平衡态热力学的统计基础与相变;5.马尔科夫过程;6.随机热力学;7.非保守朗之万系统;8.小系统热力学的Hill理论;9.Gibbs表面热力学;10.小系统热力学的研究进展。授课教师:钱紘(华盛顿大学),郑伟谋(中国科学院理论物理研究所),赵鸿(厦门大学),卢至悦(北卡罗来纳大学教堂山分校),董玮(法国里昂高师),邢向军(上海交通大学),黄亮(兰州大学)等。