◎ 理所当然 lǐsuǒdāngrán[justifiably; a matter of course; as it ought to be; be both natural and right; it goes without saying; it is what propriety requires] 按道理应该如此 就把来结识了这位大哥,也是理所当然。——明· 冯梦龙《醒世恒言》-----------------国语辞典：以理而言应当如此。《朱子语类．卷六○．孟子．尽心上》：「只是理所当然者便是性，只是人合当如此做底便是性。」《醒世恒言．卷一六．陆五汉硬留合色鞋》：「就把来结识了这位大哥，也是理所当然。」也作「理固当然」。近天经地义,理当如此反岂有此理