《中学数学》2007年第2期刊出了黄祥宏先生的“集合与简易逻辑中的几个疑点”(以下简称文[1])一文,读后受益匪浅.美中不足的是,笔者发现疑点1及其解析都存在严重的逻辑错误,今冒味指出.为了便于说明,现将文[1]的疑点1及其解析摘录如下:疑点1命题P:“菱形的对角线相等”的否定是 “High School Mathematics” 2007 the second issue of Mr. Huang Xianghong’s “collection and simple logic of a few doubt” (hereinafter referred to as the article [1]), a book benefited greatly from the fly in the ointment, the author found the doubt 1 For the sake of explanation, the doubt 1 of paper [1] and its analysis are excerpted as follows: Doubtful point 1 Proposition P: “the diagonal of rhombus is equal” is negative