When Yom Tov and Shabbat coincide, the Amida is that of Yom Tov, with Shabbat-specific insertions. Each time both Shabbat and Yom Tov are mentioned, Shabbat is mentioned first, as it is both holier and more frequent. The conclusion of the middle berakha is “Who sanctifies Shabbat, Israel, and the seasons.” Shabbat precedes Israel because the Jews are responsible for the sanctification of the festivals, but not of Shabbat. The sanctity of Shabbat stems from the time of creation and thus preceded the existence of the Jewish nation. It is fixed and enduring (Beitza 17a; above 1:3). At first glance, it would seem that two berakhot should be recited in the Amida, one for Shabbat and one for Yom Tov. Nevertheless, since both of the days demonstrate sanctity in time, they were combined into one berakha. Furthermore, the sanctity of Israel and the festivals is revealed through the fixed and enduring sanctity of Shabbat, and thus these two sanctities are in a sense only one.