A member posted a question regarding the interchangeability between 與 vs 乎as interrogative particles in Old Chinese. The original post is unfortunately lost due to "serious problems" the Wordreference Forums had earlier on Monday. Here is my response: Just as 呢 and 嗎 are different in modern Mandarin, so are 與 and 乎 in Old Chinese. Their respective linguistic environments are as follows: 1. 乎 (*wa in Old Chinese, also written 于 *wa) is a post-verbial interrogative particle. It follows a verb or an adjective (Note: In Old Chinese, there is no clear-cut between verbs and adjectives. We may consider them as a single word class). For instance, 論語：「為人謀而不忠乎？與朋友交而不信乎？ 傳不習乎？」呂氏春秋：「然則先王聖于？」忠,信,習 and 聖 belong to the "verb" class (including adjectives as well), and therefore 乎 (于) is the appropriate interrogative particle. 2. 與 (*lha in Old Chinese, also written 歟 *lha) is usually a post-nominal interrogative particle and in complementary distribution with 乎. For instance, 《史記》: 「子非三閭大夫歟? 」柳宗元《梓人傳》: 「能者用而智者謀,彼其智者歟?」大夫 and 智者 are noun phrases and therefore 歟 (與) is the correct particle. There are situations however where the noun phrase is implied but not explicitly stated. For instance, 孟子•告子: 「為是其智弗若與？」Conventionally, it is taken as 為是其智弗若[FONT=MingLiU]前[/FONT]者與and translated as "能说这是他的聪明才智不如前一个人吗" So 與 is used because of the implied noun phrase [FONT=MingLiU]前[/FONT]者 ( 前一个人). The above is only a rule of thumb applied to only Old Chinese. Since the Han Dynasty, people started to replace 與 with 乎. And eventually we have sentences like 宋. 蘇軾: 「“汝識之乎？」 . 之 is a pronoun and would have gone with 與 in Old Chinese.