How Many Watches Divide the Night

"And Gideon, and the hundred men that were with him, came to the edge of the camp at the beginning of the middle watch" (Judges 7:19). Our rabbis taught: The night has four watches; Rabbi Nathan says three. What is Rabbi Nathan's reasoning? It is written, "And Gideon, and the hundred men that were with him, came to the edge of the camp at the beginning of the middle watch" - and "middle" can only mean there is one before it and one after it [hence three in all]. And Rabbi [Yehudah the Prince], what does "middle" mean to him? The middle one among the middle ones [the night having four watches, so that the inner pair are both "middle"]. And what is Rabbi's reasoning? Rabbi Zerika said in the name of Rabbi Ami in the name of Rabbi Shimon ben Lakish: One verse says, "At midnight I rise to give thanks to You" (Psalms 119:62), and it is written, "My eyes anticipate the watches" (Psalms 119:148). How is this reconciled? The night has four watches. And Rabbi Nathan holds like Rabbi Yehoshua, as we learned in a teaching: Rabbi Yehoshua says, until the third hour [one may recite the morning Shema], for it is the way of kings' sons to rise at the third hour. Six hours of night and two of day make two watches [of the night]; Rav Ashi said: A watch and a half may also be called "watches."