"Correlation is not causation." This mantra, chanted by scientists for more than a century, has led to a virtual prohibition on causal talk. Today, that taboo is dead. The causal revolution, instigated by Judea Pearl and his colleagues, has cut through a century of confusion and established causality -- the study of cause and effect -- on a firm scientific basis. His work explains how we can know easy things, like whether it was rain or a sprinkler that made a sidewalk wet; and how to answer hard questions, like whether a drug cured an illness. Pearl's work enables us to know not just whether one thing causes another: it lets us explore the world that is and the worlds that could have been. It shows us the essence of human thought and key to artificial intelligence. Anyone who wants to understand either needs
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《定性与半定量物理学(第2版)》是北京大学物理系赵凯华教授在选修课讲义基础上编写的，全文曾在《大学物理》杂志(1988年第10期到1990年12期)刊载，深受广大读者欢迎。经作者增补修改后汇集出版。第一版出版于1991年，根据科学的最新发展，在第二版中某些章节做了较大的修改和补充。
赵凯华教授在书中把基础物理知识生动地、巧妙地与当今物理学前沿如粒子物理、生物物理、天体物理、对称性分形等等新鲜概念与课题结合起来，与物理学思想、方法及其历史发展结合起来，古今纵横、上下环宇，格调清新、启人心智，是物理爱好者和师生们不可多得的参考资料，也有利于物理教学改革的探索。
本书内容有绪论及对称性原理、量纲分析、数量级估计、自然界的物理学等四章，并有较丰富的例题。
《定性与半定量物理学(第2版)》可作为各类高等学校本科和专科物理专业及学习物理课程的其他理工农医专业大学生、研究生、有关教学或科研人员的参考读物，也可供中专、中学教师及物理爱好者阅读或作进修之用。